Apparatus for transmitting and receiving a signal and method of transmitting and receiving a signal

ABSTRACT

The present invention relates to a method of transmitting and a method of receiving signals an corresponding apparatus. One aspect of the present invention relates to an efficient L1 signaling method for an efficient transmitter and an efficient receiver using the efficient L1 signaling method for an efficient cable broadcasting.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a method for transmitting and receivinga signal and an apparatus for transmitting and receiving a signal, andmore particularly, to a method for transmitting and receiving a signaland an apparatus for transmitting and receiving a signal, which arecapable of improving data transmission efficiency.

2. Background Art

As a digital broadcasting technology has been developed, users havereceived a high definition (HD) moving image. With continuousdevelopment of a compression algorithm and high performance of hardware,a better environment will be provided to the users in the future. Adigital television (DTV) system can receive a digital broadcastingsignal and provide a variety of supplementary services to users as wellas a video signal and an audio signal.

Digital Video Broadcasting (DVB)-C2 is the third specification to joinDVB's family of second generation transmission systems. Developed in1994, today DVB-C is deployed in more than 50 million cable tunersworldwide. In line with the other DVB second generation systems, DVB-C2uses a combination of Low-density parity-check (LDPC) and BCH codes.This powerful Forward Error correction (FEC) provides about 5 dBimprovement of carrier-to-noise ratio over DVB-C. Appropriatebit-interleaving schemes optimize the overall robustness of the FECsystem. Extended by a header, these frames are called Physical LayerPipes (PLP). One or more of these PLPs are multiplexed into a dataslice. Two dimensional interleaving (in the time and frequency domains)is applied to each slice enabling the receiver to eliminate the impactof burst impairments and frequency selective interference such as singlefrequency ingress.

With the development of these digital broadcasting technologies, arequirement for a service such as a video signal and an audio signalincreased and the size of data desired by users or the number ofbroadcasting channels gradually increased.

DISCLOSURE OF INVENTION Technical Problem

Accordingly, the present invention is directed to a method fortransmitting and receiving a signal and an apparatus for transmittingand receiving a signal that substantially obviate one or more problemsdue to limitations and disadvantages of the related art.

Technical Solution

An object of the present invention is to provide a method fortransmitting and receiving a signal and an apparatus for transmittingand receiving a signal, which are capable of improving data transmissionefficiency.

Another object of the present invention is to provide a method fortransmitting and receiving a signal and an apparatus for transmittingand receiving a signal, which are capable of improving error correctioncapability of bits configuring a service.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following. The objectives and other advantages of theinvention may be realized and attained by the structure particularlypointed out in the written description and claims hereof as well as theappended drawings.

To achieve the objects, the present invention provides a transmitter fortransmitting broadcasting data to a receiver, the transmittercomprising: a first encoder configured to receive PLP(Physical LayerPipe) data, to encode the received PLP data and to output the encodedPLP data; a second encoder configured to receive Layer 1 signaling data,to encode the received Layer 1 signaling data and to output the encodedLayer 1 signaling data; and a frame builder configured to receive theoutput PLP data and the output Layer 1 signaling data and to assemblethe received PLP data and the received Layer 1 signaling data to form aframe structure, wherein the transmitter is configured to process theLayer 1 signaling data, wherein the Layer 1 signaling data includePLP_bundled information indicating whether or not the associated PLP isbundled with other PLP within a broadcasting system.

Yet another embodiment of the present invention provides a receiver forprocessing broadcasting data, the receiver comprising: a frame dividerconfigured to receive a frame having at least one PLP(Physical LayerPipe) data and a frame header and to divide the frame into the at leastone PLP data and the frame header, the frame header having Layer 1signaling data; and a decoder configured to receive the divided Layer 1signaling data and to decode the received Layer 1 signaling data,wherein the receiver is configured to process the Layer 1 signalingdata, wherein the Layer 1 signaling data include PLP_bundled informationindicating whether or not the associated PLP is bundled with other PLPwithin a broadcasting system.

Yet another embodiment of the present invention provides a method ofreceiving broadcasting data, the method comprising: receiving a framehaving at least one PLP(Physical Layer Pipe) data and a frame header;dividing the frame into the at least one PLP data and the frame header,the frame header including Layer 1 signaling data; receiving the dividedLayer 1 signaling data; and decoding the received Layer 1 signalingdata, wherein the Layer 1 signaling data include PLP_bundled informationindicating whether or not the associated PLP is bundled with other PLPwithin a broadcasting system.

Yet another embodiment of the present invention provides a method oftransmitting broadcasting signal to a receiver, the method comprising:receiving PLP(Physical Layer Pipe) data; encoding the received PLP data;receiving Layer 1 signaling data; encoding the received Layer 1signaling data; assembling the encoded PLP data and the encoded Layer 1signaling data to form a frame structure; wherein the Layer 1 signalingdata include PLP_bundled information indicating whether or not theassociated PLP is bundled with other PLP within a broadcasting system.

Advantageous Effects

According to the present invention, it is possible to provide a receiverfor processing broadcasting data, the receiver comprising: a framedivider configured to receive a frame having at least one PLP(PhysicalLayer Pipe) data and a frame header and to divide the frame into the atleast one PLP data and the frame header, the frame header having Layer 1signaling data; and a decoder configured to receive the divided Layer 1signaling data and to decode the received Layer 1 signaling data,wherein the receiver is configured to process the Layer 1 signalingdata, wherein the Layer 1 signaling data include PLP_bundled informationindicating whether or not the associated PLP is bundled with other PLPwithin a broadcasting system.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is an example of digital transmission system.

FIG. 2 is an example of an input processor.

FIG. 3 is an information that can be included in Base band (BB).

FIGS. 4( a) and 4(b) are an example of BICM module.

FIG. 5 is an example of shortened/punctured encoder.

FIG. 6 is an example of applying various constellations.

FIG. 7 is another example of cases where compatibility betweenconventional systems is considered.

FIG. 8 is a frame structure which comprises preamble for L1 signalingand data symbol for PLP data.

FIG. 9 is an example of frame builder.

FIGS. 10( a) and 10(b) are an example of pilot inserting module 404shown in FIG. 4.

FIGS. 11( a) and 11(b) are a structure of SP.

FIG. 12 is a new SP structure or Pilot Pattern (PP5′).

FIG. 13 is a suggested PP5′ structure.

FIG. 14 is a relationship between data symbol and preamble.

FIG. 15 is another relationship between data symbol and preamble.

FIG. 16 is an example of cable channel delay profile.

FIG. 17 is scattered pilot structure that uses z=56 and z=112.

FIG. 18 is an example of modulator based on OFDM.

FIG. 19 is an example of preamble structure.

FIG. 20 is an example of Preamble decoding.

FIG. 21 is a process for designing more optimized preamble.

FIG. 22 is another example of preamble structure

FIG. 23 is another example of Preamble decoding.

FIG. 24 is an example of Preamble structure.

FIG. 25 is an example of L1 decoding.

FIG. 26 is an example of analog processor.

FIG. 27 is an example of digital receiver system.

FIG. 28 is an example of analog processor used at receiver.

FIG. 29 is an example of demodulator.

FIG. 30 is an example of frame parser.

FIGS. 31( a) and 31(b) are an example of BICM demodulator.

FIG. 32 is an example of LDPC decoding using shortening/puncturing.

FIG. 33 is an example of output processor.

FIG. 34 is an example of L1 block repetition rate of 8 MHz.

FIG. 35 is an example of L1 block repetition rate of 8 MHz.

FIG. 36 is a new L1 block repetition rate of 7.61 MHz.

FIG. 37 is an example of L1 signaling which is transmitted in frameheader.

FIG. 38 is preamble and L1 Structure simulation result.

FIG. 39 is an example of symbol interleaver.

FIG. 40 is an example of an L1 block transmission.

FIG. 41 is another example of L1 signaling transmitted within a frameheader.

FIG. 42 is an example of frequency or time interleaving/deinterleaving.

FIG. 43 is a table analyzing overhead of L1 signaling which istransmitted in FECFRAME header at ModCod Header Inserting module 307 ondata path of BICM module shown in FIG. 3.

FIG. 44 is showing a structure for FECFRAME header for minimizingoverhead.

FIG. 45 is showing a bit error rate (BER) performance of theaforementioned L1 protection.

FIG. 46 is showing examples of a transmission frame and FEC framestructure.

FIG. 47 is showing an example of L1 signaling.

FIG. 48 is showing an example of L1-pre signaling.

FIG. 49 is showing a structure of L1 signaling block.

FIG. 50 is showing an L1 time interleaving.

FIG. 51 is showing an example of extracting modulation and codeinformation.

FIG. 52 is showing another example of L1-pre signaling.

FIG. 53 is showing an example of scheduling of L1 signaling block thatis transmitted in preamble.

FIG. 54 is showing an example of L1-pre signaling where power boostingis considered.

FIG. 55 is showing an example of L1 signaling.

FIG. 56 is showing another example of extracting modulation and codeinformation.

FIG. 57 is showing another example of extracting modulation and codeinformation.

FIG. 58 is showing an example of L1-pre synchronization.

FIG. 59 is showing an example of L1-pre signaling.

FIG. 60 is showing an example of L1 signaling.

FIG. 61 is showing an example of L1 signalling path.

FIG. 62 is another example of L1 signaling transmitted within a frameheader.

FIG. 63 is another example of L1 signaling transmitted within a frameheader.

FIG. 64 is another example of L1 signaling transmitted within a frameheader.

FIG. 65 is showing an example of L1 signaling.

FIG. 66 is an example of symbol interleaver.

FIG. 67 is showing an interleaving performance of time interleaver ofFIG. 66.

FIG. 68 is an example of symbol interleaver.

FIG. 69 is showing an interleaving performance of time interleaver ofFIG. 68.

FIG. 70 is an example of symbol deinterleaver.

FIG. 71 is another example of time interleaving.

FIG. 72 is a result of interleaving using method shown in FIG. 71.

FIG. 73 is an example of addressing method of FIG. 72.

FIG. 74 is another example of L1 time interleaving.

FIG. 75 is an example of symbol deinterleaver.

FIG. 76 is another example of deinterleaver.

FIG. 77 is an example of symbol deinterleaver.

FIG. 78 is an example of row and column addresses for timedeinterleaving.

FIG. 79 shows an example of general block interleaving in a data symboldomain where pilots are not used.

FIG. 80 is an example of an OFDM transmitter which uses data slices.

FIG. 81 is an example of an OFDM receiver which uses data slice.

FIG. 82 is an example of time interleaver and an example of timedeinterleaver.

FIG. 83 is an example of forming OFDM symbols.

FIGS. 84( a) to 84(c) are an example of a Time Interleaver (TI).

FIG. 85 is an example of a Time Interleaver (TI).

FIG. 86 is an example of a preamble structure at a transmitter and anexample of a process at a receiver.

FIG. 87 is an example of a process at a receiver to obtain L1_XFEC_FRAMEfrom preamble.

FIG. 88 is an example of a preamble structure at a transmitter and anexample of a process at a receiver.

FIG. 89 is an example of a Time Interleaver (TI).

FIG. 90 is an example of an OFDM transmitter using data slices.

FIG. 91 is an example of an OFDM receiver using data slices.

FIG. 92 is an example of a Time Interleaver (TI).

FIGS. 93( a) to 93(c) are an example of a Time De-Interleaver (TDI).

FIG. 94 is an example of a Time Interleaver (TI).

FIGS. 95( a) and 95(b) are an example of preamble time interleaving anddeinterleaving flow.

FIG. 96 is a Time Interleaving depth parameter in L1 header signaling.

FIGS. 97( a) and 97(b) are an example of an L1 header signaling, L1structure, and a padding method.

FIG. 98 is an example of L1 signaling.

FIG. 99 is an example of dslice_ti_depth.

FIG. 100 is an example of dslice_type.

FIG. 101 is an example of plp_type.

FIG. 102 is an example of Plp_payload_type.

FIG. 103 is an example of Plp_modcod.

FIG. 104 is an example of GI.

FIG. 105 is an example of PAPR.

FIG. 106 is an example of L1 signaling.

FIG. 107 is an example of plp_type.

FIG. 108 is an example of L1 signaling.

FIG. 109 is an example of an L1 header signaling, L1 structure, and apadding method.

FIG. 110 is an example of L1 signaling.

FIG. 111 is showing examples of fields of L1 signaling.

FIG. 112 is an example of L1 signaling.

FIG. 113 is an example of plp_type.

FIG. 114 is an example of L1 signaling and L2 signaling for normal andbundled PLP types.

FIG. 115 is an example of L1 and L2 decoding action flow of aconventional DVB-C2 receiver with 8 MHz single tuner.

FIG. 116 is an example of L1 and L2 decoding action flow of a premiumDVB-C2 receiver with multiple tuners or a wideband single tuner.

FIG. 117 is an example of an L2 signalling for C2.

FIG. 118 is an example of duration of the active OFDM symbol.

FIG. 119 is an example of guard interval values.

FIG. 120 is an example of L1 signaling.

FIG. 121 is an example of L1 block time interleaving.

Best Mode for Carrying Out the Invention

FIG. 120 is an example of L1 signaling.

FIG. 121 is an example of L1 block time interleaving.

MODE FOR THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In the following description, the term “service” is indicative of eitherbroadcast contents which can be transmitted/received by the signaltransmission/reception apparatus.

FIG. 1 shows an example of digital transmission system according to anembodiment of the present invention. Inputs can comprise a number ofMPEG-TS streams or GSE (General Stream Encapsulation) streams. An inputprocessor 101 can add transmission parameters to input stream andperform scheduling for a BICM module 102. The BICM module 102 can addredundancy and interleave data for transmission channel errorcorrection. A frame builder 103 can build frames by adding physicallayer signaling information and pilots. A modulator 104 can performmodulation on input symbols in efficient methods. An analog processor105 can perform various processes for converting input digital signalsinto output analog signals.

FIG. 2 shows an example of an input processor. Input MPEG-TS or GSEstream can be transformed by input preprocessor into a total of nstreams which will be independently processed. Each of those streams canbe either a complete TS frame which includes multiple service componentsor a minimum TS frame which includes service component (i.e., video oraudio). In addition, each of those streams can be a GSE stream whichtransmits either multiple services or a single service.

Input interface 202-1 can allocate a number of input bits equal to themaximum data field capacity of a Baseband (BB) frame. A padding may beinserted to complete the LDPC/BCH code block capacity. The input streamsynchronizer 203-1 can provide a mechanism to regenerate, in thereceiver, the clock of the Transport Stream (or packetized GenericStream), in order to guarantee end-to-end constant bit rates and delay.

In order to allow the Transport Stream recombining without requiringadditional memory in the receiver, the input Transport Streams aredelayed by delay compensator 204-1˜n considering interleaving parametersof the data PLPs in a group and the corresponding common PLP. Nullpacket deleting module 205-1˜n can increase transmission efficiency byremoving inserted null packet for a case of VBR (variable bit rate)service. Cyclic Redundancy Check (CRC) encoder modules 206-1˜n can addCRC parity to increase transmission reliability of BB frame. BB headerinsert (207-1˜n) modules can add BB frame header at a beginning portionof BB frame. Information that can be included in BB header is shown inFIG. 3.

A Merger/slicer module 208 can perform BB frame slicing from each PLP,merging BB frames from multiple PLPs, and scheduling each BB framewithin a transmission frame. Therefore, the merger/slicer module 208 canoutput L1 signaling information which relates to allocation of PLP inframe. Lastly, a BB scrambler module 209 can randomize input bitstreamsto minimize correlation between bits within bitstreams. The modules inshadow in FIG. 2 are modules used when transmission system uses a singlePLP, the other modules in FIG. 2 are modules used when the transmissiondevice uses multiple PLPs.

FIG. 4 shows an embodiment of BICM module according to the presentinvention. FIG. 4( a) shows a BICM for a data path and FIG. 4( b) showsa BICM for L1 signaling path.

Referring to FIG. 4( a), an outer coder 301 and an inner coder 303 canadd redundancy to input bitstreams for error correction. An outerinterleaver 302 and an inner interleaver 304 can interleave bits toprevent burst error. The Outer interleaver 302 can be omitted if theBICM is specifically for DVB-C2. A bit demux 305 can control reliabilityof each bit output from the inner interleaver 304. A symbol mapper 306can map input bitstreams into symbol streams. At this time, it ispossible to use any of a conventional QAM, an MQAM which uses theaforementioned BRGC for performance improvement, an NU-QAM which usesNon-uniform modulation, or an NU-MQAM which uses Non-uniform modulationapplied BRGC for performance improvement. To construct a system which ismore robust against noise, combinations of modulations using MQAM and/orNU-MQAM depending on the code rate of the error correction code and theconstellation capacity can be considered. At this time, the Symbolmapper 306 can use a proper constellation according to the code rate andconstellation capacity. FIG. 6 shows an example of such combinations.

Case 1 shows an example of using only NU-MQAM at low code rate forsimplified system implementation. Case 2 shows an example of usingoptimized constellation at each code rate. The transmitter can sendinformation about the code rate of the error correction code and theconstellation capacity to the receiver such that the receiver can use anappropriate constellation. FIG. 7 shows another example of cases wherecompatibility between conventional systems is considered. In addition tothe examples, further combinations for optimizing the system arepossible.

The ModCod Header inserting module 307 shown in FIG. 4 can take Adaptivecoding and modulation (ACM)/Variable coding and modulation (VCM)feedback information and add parameter information used in coding andmodulation to a FEC block as header. The Modulation type/Coderate(ModCod) header can include the following information:

-   -   FEC type (1 bits)—long or short LDPC    -   Coderate (3 bits)    -   Modulation (3 bits)—up-to 64K QAM    -   PLP identifier (8 bits)

The Symbol interleaver 308 can perform interleaving in symbol domain toobtain additional interleaving effects. Similar processes performed ondata path can be performed on L1 signaling path but with possiblydifferent parameters 301-1˜308-1. At this point, a shortened/puncturedcoder 303-1 can be used for inner code.

FIG. 5 shows an example of LDPC encoding using shortening/puncturing.Shortening process can be performed on input blocks which have less bitsthan a required number of bits for LDPC encoding as many zero bitsrequired for LDPC encoding can be padded by the zero padding module 301c. Zero Padded input bitstreams can have parity bits through LDPCencoder 302 c. At this time, for bitstreams that correspond to originalbitstreams, zeros can be removed (303 c) and for parity bitstreams,puncturing can be performed according to code-rates by the paritypuncturing module 304 c. These processed information bitstreams andparity bitstreams can be multiplexed into original sequences andoutputted by the Mux 305 c.

FIG. 8 shows a frame structure which comprises preamble for L1 signalingand data symbol for PLP data. It can be seen that preamble and datasymbols are cyclically generated, using one frame as a unit. Datasymbols comprise PLP type 0 which is transmitted using a fixedmodulation/coding and PLP type 1 which is transmitted using a variablemodulation/coding. For PLP type 0, information such as modulation, FECtype, and FEC code rate are transmitted in preamble (see FIG. 9 forFrame header inserting module 401). For PLP type 1, correspondinginformation can be transmitted in FEC block header of a data symbol (seeFIG. 3 for ModCod header inserting module 307). By the separation of PLPtypes, ModCod overhead can be reduced by 3˜4% from a total transmissionrate, for PLP type0 which is transmitted at a fixed bit rate. At areceiver, for fixed modulation/coding PLP of PLP type 0, Frame headerremover r401 shown in FIG. 30 can extract information on Modulation andFEC code rate and provide the extracted information to a BICM decodingmodule. For variable modulation/coding PLP of PLP type 1, ModCodextractor r307, r307-1 shown in FIG. 31 can extract and provide theparameters necessary for BICM decoding.

FIG. 9 shows an example of a frame builder. A frame header insertingmodule 401 can form a frame from input symbol streams and can add frameheader at front of each transmitted frame. The frame header can includethe following information:

-   -   Number of bonded channels (4 bits)    -   Guard interval (2 bits)    -   PAPR (2 bits)    -   Pilot pattern (2 bits)    -   Digital System identification (16 bits)    -   Frame identification (16 bits)    -   Frame length (16 bits)—number of Orthogonal Frequency Division        Multiplexing (OFDM) symbols per frame    -   Superframe length (16 bits)—number of frames per superframe    -   number of PLPs (8 bits)    -   for each PLP

PLP identification (8 bits)

Channel bonding id (4 bits)

PLP start (9 bits)

PLP type (2 bits)—common PLP or others

PLP payload type (5 bits)

MC type (1 bit)—fixed/variable modulation & coding

if MC type==fixed modulation & coding

FEC type (1 bits)—long or short LDPC

Coderate (3 bits)

Modulation (3 bits)—up-to 64K QAM

end if;

Number of notch channels (2 bits)

for each notch

Notch start (9 bits)

Notch width (9 bits)

end for;

PLP width (9 bits)—max number of FEC blocks of PLP

PLP time interleaving type (2 bits end for;

-   -   CRC-32 (32 bits)

Channel bonding environment is assumed for L1 information transmitted inFrame header and data that correspond to each data slice is defined asPLP. Therefore, information such as PLP identifier, channel bondingidentifier, and PLP start address are required for each channel used inbonding. One embodiment of this invention suggests transmitting ModCodfield in FEC frame header if PLP type supports variablemodulation/coding and transmitting ModCod field in Frame header if PLPtype supports fixed modulation/coding to reduce signaling overhead. Inaddition, if a Notch band exists for each PLP, by transmitting the startaddress of the Notch and its width, decoding corresponding carriers atthe receiver can become unnecessary.

FIG. 10 shows an example of Pilot Pattern (PP5) applied in a channelbonding environment. As shown, if SP positions are coincident withpreamble pilot positions, irregular pilot structure can occur.

FIG. 10( a) shows an example of pilot inserting module 404 as shown inFIG. 9. As represented in FIG. 10( a), if a single frequency band (forexample, 8 MHz) is used, the available bandwidth is 7.61 MHz, but ifmultiple frequency bands are bonded, guard bands can be removed, thus,frequency efficiency can increase greatly. FIG. 10( b) is an example ofpreamble inserting module 504 as shown in FIG. 18 that is transmitted atthe front part of the frame and even with channel bonding, the preamblehas repetition rate of 7.61 MHz, which is bandwidth of L1 block. This isa structure considering the bandwidth of a tuner which performs initialchannel scanning.

Pilot Patterns exist for both Preamble and Data Symbols. For datasymbol, scattered pilot (SP) patterns can be used. Pilot Pattern (PP5)and Pilot Pattern (PP7) of T2 can be good candidates for frequency-onlyinterpolation. PP5 has x=12, y=4, z=48 for GI= 1/64 and PP7 has x=24,y=4, z=96 for GI= 1/128. Additional time-interpolation is also possiblefor a better channel estimation. Pilot patterns for preamble can coverall possible pilot positions for initial channel acquisition. Inaddition, preamble pilot positions should be coincident with SPpositions and a single pilot pattern for both the preamble and the SP isdesired. Preamble pilots could also be used for time-interpolation andevery preamble could have an identical pilot pattern. These requirementsare important for C2 detection in scanning and necessary for frequencyoffset estimation with scrambling sequence correlation. In a channelbonding environment, the coincidence in pilot positions should also bekept for channel bonding because irregular pilot structure may degradeinterpolation performance.

In detail, if a distance z between scattered pilots (SPs) in an OFDMsymbol is 48 and if a distance y between SPs corresponding to a specificSP carrier along the time axis is 4, an effective distance x after timeinterpolation becomes 12. This is when a guard interval (GI) fraction is1/64. If GI fraction is 1/128, x=24, y=4, and z=96 can be used. Ifchannel bonding is used, SP positions can be made coincident withpreamble pilot positions by generating non-continuous points inscattered pilot structure.

At this time, preamble pilot positions can be coincident with every SPpositions of data symbol. When channel bonding is used, data slice wherea service is transmitted, can be determined regardless of 8 MHzbandwidth granularity. However, for reducing overhead for data sliceaddressing, transmission starting from SP position and ending at SPposition can be chosen.

When a receiver receives such SPs, if necessary, channel estimation(r501) shown in FIG. 29 can perform time interpolation to obtain pilotsshown in dotted lines in FIGS. 10 and 10 and perform frequencyinterpolation. At this time, for non-continuous points of whichintervals are designated as ‘32’ in FIG. 10( a), either performinginterpolations on left and right separately or performing interpolationson only one side then performing interpolation on the other side byusing the already interpolated pilot positions of which interval is 12as a reference point can be implemented. At this time, data slice widthcan vary within 7.61 MHz, thus, a receiver can minimize powerconsumption by performing channel estimation and decoding only necessarysubcarriers.

FIG. 11 shows another example of PP5 applied in channel bondingenvironment or a structure of SP for maintaining effective distance x as12 to avoid irregular SP structure shown in FIG. 10 when channel bondingis used. As shown, if SP distance is kept consistent in case of channelbonding, there will be no problem in frequency interpolation but pilotpositions between data symbol and preamble may not be coincident. Inother words, this structure does not require additional channelestimation for an irregular SP structure, however, SP positions used inchannel bonding and preamble pilot positions become different for eachchannel.

FIG. 12 shows a new SP structure or PP5′ to provide a solution to thetwo problems aforementioned in channel bonding environment.Specifically, a pilot distance of x=16 can solve those problems. Topreserve pilot density or to maintain the same overhead, a PP5′ can havex=16, y=3, z=48 for GI= 1/64 and a PP7′ can have x=16, y=6, z=96 for GI=1/128. Frequency-only interpolation capability can still be maintained.Pilot positions are depicted in FIG. 12 for comparison with PP5structure.

FIG. 13 shows an example of a new SP Pattern or PP5′ structure inchannel bonding environment. As shown in FIG. 46, whether either singlechannel or channel bonding is used, an effective pilot distance x=16 canbe provided. In addition, because SP positions can be made coincidentwith preamble pilot positions, channel estimation deterioration causedby SP irregularity or non-coincident SP positions can be avoided. Inother words, no irregular SP position exists for freq-interpolator andcoincidence between preamble and SP positions is provided.

Consequently, the proposed new SP patterns can be advantageous in thatsingle SP pattern can be used for both single and bonded channel; noirregular pilot structure can be caused, thus a good channel estimationis possible; both preamble and SP pilot positions can be keptcoincident; pilot density can be kept the same as for PP5 and PP7respectively; and Frequency-only interpolation capability can also bepreserved.

In addition, the preamble structure can meet the requirements such aspreamble pilot positions should cover all possible SP positions forinitial channel acquisition; maximum number of carriers should be 3409(7.61 MHz) for initial scanning; exactly same pilot patterns andscrambling sequence should be used for C2 detection; and nodetection-specific preamble like P1 in T2 is required.

In terms of relation with frame structure, data slice positiongranularity may be modified to 16 carriers rather than 12, thus, lessposition addressing overhead can occur and no other problem regardingdata slice condition, Null slot condition etc can be expected.

Therefore, at channel estimation module r501 of FIG. 62, pilots in everypreamble can be used when time interpolation of SP of data symbol isperformed. Therefore, channel acquisition and channel estimation at theframe boundaries can be improved.

Now, regarding requirements related to the preamble and the pilotstructure, there is consensus in that positions of preamble pilots andSPs should coincide regardless of channel bonding; the number of totalcarriers in L1 block should be dividable by pilot distance to avoidirregular structure at band edge; L1 blocks should be repeated infrequency domain; and L1 blocks should always be decodable in arbitrarytuner window position. Additional requirements would be that pilotpositions and patterns should be repeated by period of 8 MHz; correctcarrier frequency offset should be estimated without channel bondingknowledge; and L1 decoding (re-ordering) is impossible before thefrequency offset is compensated.

FIG. 14 shows a relationship between data symbol and preamble whenpreamble structures as shown in FIG. 19 and FIG. 20 are used. L1 blockcan be repeated by period of 6 MHz. For L1 decoding, both frequencyoffset and Preamble shift pattern should be found. L1 decoding is notpossible in arbitrary tuner position without channel bonding informationand a receiver cannot differentiate between preamble shift value andfrequency offset.

Thus, a receiver, specifically for Frame header remover (r401) shown inFIG. 30 to perform L1 signal decoding, channel bonding structure needsto be obtained. Because preamble shift amount expected at two verticallyshadowed regions in FIG. 30 is known, time/freq synchronizer r505 inFIG. 29 can estimate carrier frequency offset. Based on the estimation,L1 signaling path r308-1˜r301-1 in FIG. 31 can decode L1 block.

FIG. 15 shows a relationship between data symbol and preamble when thepreamble structure as shown in FIG. 22 is used. L1 block can be repeatedby period of 8 MHz. For L1 decoding, only frequency offset needs to befound and channel bonding knowledge may not be required. Frequencyoffset can be easily estimated by using known Pseudo Random BinarySequence (PRBS) sequence. As shown in FIG. 48, preamble and data symbolsare aligned, thus, additional sync search can become unnecessary.Therefore, for a receiver, specifically for the Frame header removerr401 shown in FIG. 63, it is possible that only correlation peak withpilot scrambling sequence needs to be obtained to perform L1 signaldecoding. The time/freq synchronizer r505 in FIG. 29 can estimatecarrier frequency offset from peak position.

FIG. 16 shows an example of cable channel delay profile.

From the point of view of pilot design, current GI already over-protectsdelay spread of cable channel. In the worst case, redesigning thechannel model can be an option. To repeat the pattern exactly every 8MHz, the pilot distance should be a divisor of 3584 carriers (z=32 or56). A pilot density of z=32 can increase pilot overhead, thus, z=56 canbe chosen. Slightly less delay coverage may not be an important in cablechannel. For example, it can be 8 μs for PP5′ and 4 μs for PP7′ comparedto 9.3 μs (PP5) and 4.7 μs (PP7). Meaningful delays can be covered byboth pilot patterns even in a worst case. For preamble pilot position,no more than all SP positions in data symbol are necessary.

If the −40 dB delay path can be ignored, actual delay spread can become2.5 us, 1/64 GI=7 μs, or 1/128 GI=3.5 μs. This shows that pilot distanceparameter, z=56 can be a good enough value. In addition, z=56 can be aconvenient value for structuring pilot pattern that enables preamblestructure shown in FIG. 48.

FIG. 17 shows scattered pilot structure that uses z=56 and z=112 whichis constructed at pilot inserting module 404 in FIG. 42. PP5′ (x=14,y=4, z=56) and PP7′ (x=28, y=4, z=112) are proposed. Edge carriers couldbe inserted for closing edge.

As shown in FIG. 50, pilots are aligned at 8 MHz from each edge of theband, every pilot position and pilot structure can be repeated every 8MHz. Thus, this structure can support the preamble structure shown inFIG. 48. In addition, a common pilot structure between preamble and datasymbols can be used. Therefore, channel estimation module r501 in FIG.29 can perform channel estimation using interpolation on preamble anddata symbols because no irregular pilot pattern can occur, regardless ofwindow position which is decided by data slice locations. At this time,using only frequency interpolation can be enough to compensate channeldistortion from delay spread. If time interpolation is performedadditionally, more accurate channel estimation can be performed.

Consequently, in the new proposed pilot pattern, pilot position andpattern can be repeated based on a period of 8 MHz. A single pilotpattern can be used for both preamble and data symbols. L1 decoding canalways be possible without channel bonding knowledge. In addition, theproposed pilot pattern may not affect commonality with T2 because thesame pilot strategy of scattered pilot pattern can be used; T2 alreadyuses 8 different pilot patterns; and no significant receiver complexitycan be increased by modified pilot patterns. For a pilot scramblingsequence, the period of PRBS can be 2047 (m-sequence); PRBS generationcan be reset every 8 MHz, of which the period is 3584; pilot repetitionrate of 56 can be also co-prime with 2047; and no PAPR issue can beexpected.

FIG. 18 shows an example of a modulator based on OFDM. Input symbolstreams can be transformed into time domain by IFFT module 501. Ifnecessary, peak-to-average power ratio (PAPR) can be reduced at PAPRreducing module 502. For PAPR methods, Active constellation extension(ACE) or tone reservation can be used. GI inserting module 503 can copya last part of effective OFDM symbol to fill guard interval in a form ofcyclic prefix.

Preamble inserting module 504 can insert preamble at the front of eachtransmitted frame such that a receiver can detect digital signal, frameand acquire time/freq offset acquisition. At this time, the preamblesignal can perform physical layer signaling such as FFT size (3 bits)and Guard interval size (3 bits). The Preamble inserting module 504 canbe omitted if the modulator is specifically for DVB-C2.

FIG. 19 shows an example of a preamble structure for channel bonding,generated at preamble inserting module 504 in FIG. 51. One complete L1block should be “always decodable” in any arbitrary 7.61 MHz tuningwindow position and no loss of L1 signaling regardless of tuner windowposition should occur. As shown, L1 blocks can be repeated in frequencydomain by period of 6 MHz. Data symbol can be channel bonded for every 8MHz. If, for L1 decoding, a receiver uses a tuner such as the tuner r603represented in FIG. 28 which uses a bandwidth of 7.61 MHz, the Frameheader remover r401 in FIG. 30 needs to rearrange the received cyclicshifted L1 block (FIG. 20) to its original form. This rearrangement ispossible because L1 block is repeated for every 6 MHz block.

FIG. 21 shows a process for designing a more optimized preamble. Thepreamble structure of FIG. 19 uses only 6 MHz of total tuner bandwidth7.61 MHz for L1 decoding. In terms of spectrum efficiency, tunerbandwidth of 7.61 MHz is not fully utilized. Therefore, there can befurther optimization in spectrum efficiency.

FIG. 22 shows another example of preamble structure or preamble symbolsstructure for full spectrum efficiency, generated at Frame HeaderInserting module 401 in FIG. 42. Just like data symbol, L1 blocks can berepeated in frequency domain by period of 8 MHz. One complete L1 blockis still “always decodable” in any arbitrary 7.61 MHz tuning windowposition. After tuning, the 7.61 MHz data can be regarded as a virtuallypunctured code. Having exactly the same bandwidth for both the preambleand data symbols and exactly the same pilot structure for both thepreamble and data symbols can maximize spectrum efficiency. Otherfeatures such as cyclic shifted property and not sending L1 block incase of no data slice can be kept unchanged. In other words, thebandwidth of preamble symbols can be identical with the bandwidth ofdata symbols or, as shown in FIG. 57, the bandwidth of the preamblesymbols can be the bandwidth of the tuner (here, it's 7.61 MHz). Thetuner bandwidth can be defined as a bandwidth that corresponds to anumber of total active carriers when a single channel is used. That is,the bandwidth of the preamble symbol can correspond to the number oftotal active carriers (here, it's 7.61 MHz).

FIG. 23 shows a virtually punctured code. The 7.61 MHz data among the 8MHz L1 block can be considered as punctured coded. When a tuner r603shown in FIG. 28 uses 7.61 MHz bandwidth for L1 decoding, Frame headerremover r401 in FIG. 30 needs to rearrange received, cyclic shifted L1block into original form as shown in FIG. 56. At this time, L1 decodingis performed using the entire bandwidth of the tuner. Once the L1 blockis rearranged, a spectrum of the rearranged L1 block can have a blankregion within the spectrum as shown in upper right side of FIG. 23because an original size of L1 block is 8 MHz bandwidth.

Once the blank region is zero padded, either after deinterleaving insymbol domain by the freq. deinterleaver r403 in FIG. 30 or by thesymbol deinterleaver r308-1 in FIG. 31 or after deinterleaving in bitdomain by the symbol demapper r306-1, bit mux r305-1, and innerdeinterleaver r304-1 in FIG. 31, the block can have a form which appearsto be punctured as shown in lower right side of FIG. 23.

This L1 block can be decoded at the punctured/shortened decoding moduler303-1 in FIG. 31. By using these preamble structure, the entire tunerbandwidth can be utilized, thus spectrum efficiency and coding gain canbe increased. In addition, an identical bandwidth and pilot structurecan be used for the preamble and data symbols.

In addition, if the preamble bandwidth or the preamble symbols bandwidthis set as a tuner bandwidth as shown in FIG. 25, (it's 7.61 MHz in theexample), a complete L1 block can be obtained after rearrangement evenwithout puncturing. In other words, for a frame having preamble symbols,wherein the preamble symbols have at least one layer 1 (L1) block, itcan be said, the L1 block has 3408 active subcarriers and the 3408active subcarriers correspond to 7.61 MHz of 8 MHz Radio Frequency (RF)band.

Thus, spectrum efficiency and L1 decoding performance can be maximized.In other words, at a receiver, decoding can be performed atpunctured/shortened decoding module block r303-1 in FIG. 31, afterperforming only deinterleaving in the symbol domain.

Consequently, the proposed new preamble structure can be advantageous inthat it's fully compatible with previously used preamble except that thebandwidth is different; L1 blocks are repeated by period of 8 MHz; L1block can be always decodable regardless of tuner window position; Fulltuner bandwidth can be used for L1 decoding; maximum spectrum efficiencycan guarantee more coding gain; incomplete L1 block can be considered aspunctured coded; simple and same pilot structure can be used for bothpreamble and data; and identical bandwidth can be used for both preambleand data.

FIG. 26 shows an example of an analog processor. A DAC (601) can convertdigital signal input into analog signal. After transmission frequencybandwidth is up-converted at up-converter 602 and analog filtered signalthrough analog filter 603 can be transmitted.

FIG. 27 shows an example of a digital receiver system according to anembodiment of the present invention. Received signal is converted intodigital signal at an analog processor r105. A demodulator r104 canconvert the signal into data in frequency domain. A frame parser r103can remove pilots and headers and enable selection of serviceinformation that needs to be decoded. A BICM demodulator r102 cancorrect errors in the transmission channel. An output processor r101 canrestore the originally transmitted service stream and timinginformation.

FIG. 28 shows an example of analog processor used at the receiver. ATuner/AGC (Auto gain controller) module r603 can select desiredfrequency bandwidth from received signal. A down converter r602 canrestore baseband. An ADC r601 can convert analog signal into digitalsignal.

FIG. 29 shows an example of demodulator. A frame detector r506 candetect the preamble, check if a corresponding digital signal exists, anddetect a start of a frame. A time/freq synchronizer r505 can performsynchronization in time and frequency domains. At this time, for timedomain synchronization, a guard interval correlation can be used. Forfrequency domain synchronization, correlation can be used or offset canbe estimated from phase information of a subcarrier that is transmittedin the frequency domain. A preamble remover r504 can remove preamblefrom the front of detected frame. A GI remover r503 can remove guardinterval. A FFT module r501 can transform signal in the time domain intosignal in the frequency domain. A channel estimation/equalization moduler501 can compensate errors by estimating distortion in transmissionchannel using pilot symbol. The Preamble remover r504 can be omitted ifthe demodulator is specifically for DVB-C2.

FIG. 30 shows an example of frame parser. A pilot remove (r404) canremove pilot symbol. A frequency deinterleaver r403 can performdeinterleaving in the frequency domain. An OFDM symbol merger r402 canrestore data frame from symbol streams transmitted in OFDM symbols. Aframe header remover r401 can extract physical layer signaling fromheader of each transmitted frame and remove header. Extractedinformation can be used as parameters for following processes in thereceiver.

FIG. 31 shows an example of a BICM demodulator. FIG. 31( a) shows a datapath and FIG. 31( b) shows a L1 signaling path. A symbol deinterleaverr308 can perform deinterleaving in the symbol domain. A ModCod extractorr307 can extract ModCod parameters from front of each BB frame and makethe parameters available for following adaptive/variable demodulationand decoding processes. A Symbol demapper r306 can demap input symbolstreams into bit Log-Likelihood Ratio (LLR) streams. The Output bit LLRstreams can be calculated by using a constellation used in a Symbolmapper 306 of the transmitter as reference point. At this point, whenthe aforementioned MQAM or NU-MQAM is used, by calculating both I axisand Q axis when calculating bit nearest from MSB and by calculatingeither I axis or Q axis when calculating the rest bits, an efficientsymbol demapper can be implemented. This method can be applied to, forexample, Approximate LLR, Exact LLR, or Hard decision.

When an optimized constellation according to constellation capacity andcode rate of error correction code at the Symbol mapper 306 of thetransmitter is used, the Symbol demapper r306 of the receiver can obtaina constellation using the code rate and constellation capacityinformation transmitted from the transmitter. The bit mux r305 of thereceiver can perform an inverse function of the bit demux 305 of thetransmitter. The Inner deinterleaver r304 and outer deinterleaver r302of the receiver can perform inverse functions of the inner interleaver(304) and outer interleaver 302 of the transmitter, respectively to getthe bitstream in its original sequence. The outer deinterleaver r302 canbe omitted if the BICM demodulator is specifically for DVB-C2.

The inner decoder r303 and outer decoder r301 of the receiver canperform corresponding decoding processes to the inner coder 303 andouter coder 301 of the transmitter, respectively, to correct errors inthe transmission channel. Similar processes performed on data path canbe performed on L1 signaling path, but with different parametersr308-1˜r301-1. At this point, as explained in the preamble part, ashortened/punctured coding module r303-1 can be used for L1 signaldecoding.

FIG. 32 shows an example of LDPC decoding using shortening/puncturingmodule r303-1. A demux r301 a can separately output information part andparity part of systematic code from input bit streams. For theinformation part, a zero padding module r302 a can perform zero paddingaccording to a number of input bit streams of LDPC decoder, and for theparity part, input bit streams for the LDPC decoder can be generated byde-puncturing the punctured part at the parity depuncturing module r303a. LDPC decoding by the module r304 a can be performed on generated bitstreams, and zeros in information part can be removed by the zeroremover r305 a and outputted.

FIG. 33 shows an example of output processor. A BB descrambler r209 canrestore scrambled bit streams at the transmitter. A Splitter r208 canrestore BB frames that correspond to multiple PLP that are multiplexedand transmitted from the transmitter according to PLP path. For each PLPpath, a BB header removers r207-1˜n can remove the header that istransmitted at the front of the BB frame. A CRC decoder r206-1˜n canperform CRC decoding and make reliable BB frames available forselection. A Null packet inserting module r205-1˜n can restore nullpackets which were removed for higher transmission efficiency in theiroriginal location. A Delay recovering module r204-1˜n can restore adelay that exists between each PLP path.

An output clock recovering module r203-1˜n can restore the originaltiming of the service stream from timing information transmitted fromthe input stream synchronizer 203-1˜n. An output interface moduler202-1˜n can restore data in TS/GS packet from input bit streams thatare sliced in BB frame. An output postprocessor r201-1˜n can restoremultiple TS/GS streams into a complete TS/GS stream, if necessary. Theshaded blocks shown in FIG. 33 represent modules that can be used when asingle PLP is processed at a time and the rest of the blocks representmodules that can be used when multiple PLPs are processed at the sametime.

Preamble pilot patterns were carefully designed to avoid PAPR increase,thus, whether L1 repetition rate may increase PAPR needs to beconsidered. The number of L1 information bits varies dynamicallyaccording to the channel bonding, the number of PLPs, etc. In detail, itis necessary to consider things such as fixed L1 block size mayintroduce unnecessary overhead; L1 signaling should be protected morestrongly than data symbols; and time interleaving of L1 block canimprove robustness over channel impairment such as impulsive noise need.

For a L1 block repetition rate of 8 MHz, as shown in FIG. 34, fullspectrum efficiency (26.8% BW increase) is exhibited with virtualpuncturing but the PAPR may be increased since L1 bandwidth is the sameas that of the data symbols. For the repetition rate of 8 MHz, 4K-FFTDVB-T2 frequency interleaving can be used for commonality and the samepattern can repeat itself at a 8 MHz period after interleaving.

For a L1 block repetition rate of 6 MHz, as shown in FIG. 35, reducedspectrum efficiency can be exhibited with no virtual puncturing. Asimilar problem of PAPR as for the 8 MHz case can occur since the L1 anddata symbol bandwidths share LCM=24 MHz. For the repetition rate of 6MHz, 4K-FFT DVB-T2 frequency interleaving can be used for commonalityand the same pattern can repeat itself at a period of 24 MHz afterinterleaving.

FIG. 36 shows a new L1 block repetition rate of 7.61 MHz or full tunerbandwidth.

A full spectrum efficiency (26.8% BW increase) can be obtained with novirtual puncturing. There can be no PAPR issue since L1 and data symbolbandwidths share LCM≈1704 MHz. For the repetition rate of 7.61 MHz,4K-FFT DVB-T2 frequency interleaving can be used for commonality and thesame pattern can repeat itself by period of about 1704 MHz afterinterleaving.

FIG. 37 is an example of L1 signaling which is transmitted in the frameheader. Each information in L1 signaling can be transmitted to thereceiver and can be used as a decoding parameter. Especially, theinformation can be used in L1 signal path shown in FIG. 31 and PLPs canbe transmitted in each data slice. An increased robustness for each PLPcan be obtained.

FIG. 39 is an example of a symbol interleaver 308-1 as shown in L1signaling path in FIG. 4 and also can be an example of its correspondingsymbol deinterleaver r308-1 as shown in L1 signaling path in FIG. 31.Blocks with tilted lines represent L1 blocks and solid blocks representdata carriers. L1 blocks can be transmitted not only within a singlepreamble, but also can be transmitted within multiple OFDM blocks.Depending on a size of L1 block, the size of the interleaving block canvary. In other words, num_L1_sym and L1_span can be different from eachother. To minimize unnecessary overhead, data can be transmitted withinthe rest of the carriers of the OFDM symbols where the L1 block istransmitted. At this point, full spectrum efficiency can be guaranteedbecause the repeating cycle of L1 block is still a full tuner bandwidth.In FIG. 39, the numbers in blocks with tilted lines represent the bitorder within a single LDPC block.

Consequently, when bits are written in an interleaving memory in the rowdirection according to a symbol index as shown in FIG. 72 and read inthe column direction according to a carrier index, a block interleavingeffect can be obtained. In other words, one LDPC block can beinterleaved in the time domain and the frequency domain and then can betransmitted. Num_L1_sym can be a predetermined value, for example, anumber between 2˜4 can be set as a number of OFDM symbols. At thispoint, to increase the granularity of the L1 block size, apunctured/shortened LDPC code having a minimum length of the codewordcan be used for L1 protection.

FIG. 40 is an example of an L1 block transmission. FIG. 40 illustratesFIG. 39 in frame domain. As shown on the left side of FIG. 40, L1 blockscan be spanning in full tuner bandwidth or as shown on the right side ofFIG. 40, L1 blocks can be partially spanned and the rest of the carrierscan be used for data carrier. In either case, it can be seen that therepetition rate of L1 block can be identical to a full tuner bandwidth.In addition, for OFDM symbols which uses L1 signaling includingpreamble, only symbol interleaving can be performed while not allowingdata transmission in that OFDM symbols. Consequently, for OFDM symbolused for L1 signaling, a receiver can decode L1 by performingdeinterleaving without data decoding. At this point, the L1 block cantransmit L1 signaling of current frame or L1 signaling of a subsequentframe. At the receiver side, L1 parameters decoded from L1 signalingdecoding path shown in FIG. 31 can be used for decoding process for datapath from frame parser of subsequent frame.

In summary, at a transmitter, interleaving blocks of L1 region can beperformed by writing blocks to a memory in a row direction and readingthe written blocks from the memory in a column direction. At a receiver,deinterleaving blocks of L1 region can be performed by writing blocks toa memory in a column direction and reading the written blocks from thememory in a row direction. The reading and writing directions oftransmitter and receiver can be interchanged.

When simulation is performed with assumptions such as CR=½ for L1protection and for T2 commonality; 16-QAM symbol mapping; pilot densityof 6 in the Preamble; number of short LDPC implies required amount ofpuncturing/shortening are made, results or conclusions such as onlypreamble for L1 transmission may not be sufficient; the number of OFDMsymbols depends on the amount of L1 block size; shortest LDPC codeword(e.g. 192 bits information) among shortened/punctured code may be usedfor flexibility and fine granularity; and Padding may be added ifrequired with negligible overhead, can be obtained. The result issummarized in FIG. 38.

Consequently, for a L1 block repetition rate, full tuner bandwidth withno virtual puncturing can be a good solution and still no PAPR issue canarise with full spectrum efficiency. For L1 signaling, efficientsignaling structure can allow maximum configuration in an environment of8 channels bonding, 32 notches, 256 data slices, and 256 PLPs. For L1block structure, flexible L1 signaling can be implemented according toL1 block size. Time interleaving can be performed for better robustnessfor T2 commonality. Less overhead can allow data transmission inpreamble.

Block interleaving of L1 block can be performed for better robustness.The interleaving can be performed with fixed pre-defined number of L1symbols (num_L1_sym) and a number of carriers spanned by L1 as aparameter (L1_span). The same technique is used for P2 preambleinterleaving in DVB-T2.

L1 block of variable size can be used. Size can be adaptable to theamount of L1 signaling bits, resulting in a reduced overhead. Fullspectrum efficiency can be obtained with no PAPR issue. Less than 7.61MHz repetition can mean that more redundancy can be sent but unused. NoPAPR issue can arise because of 7.61 MHz repetition rate for L1 block.

FIG. 41 is another example of L1 signaling transmitted within a frameheader. FIG. 41 is different from FIG. 37 in that the L1_span fieldhaving 12 bits it is divided into two fields. In other words, theL1_span field is divided into a L1_column having 9 bits and a L1_rowhaving 3 bits. The L1_column represents the carrier index that L1_spans.Because data slice starts and ends at every 12 carriers, which is thepilot density, the 12 bits of overhead can be reduced by 3 bits to reach9 bits.

L1_row represents the number of OFDM symbols where L1 is spanning whentime interleaving is applied. Consequently, time interleaving can beperformed within an area of L1_columns multiplied by L1_rows.Alternatively, a total size of L1 blocks can be transmitted such thatL1_span shown in FIG. 37 can be used when time interleaving is notperformed. For such a case, L1 block size is 11,776×2 bits in theexample, thus 15 bits is enough. Consequently, the L1_span field can bemade up of 15 bits.

FIG. 42 is an example of frequency or time interleaving/deinterleaving.FIG. 42 shows a part of a whole transmission frame. FIG. 42 also showsbonding of multiple 8 MHz bandwidths. A frame can consist of a preamblewhich transmits L1 blocks and a data symbol which transmits data. Thedifferent kinds of data symbols represent data slices for differentservices. As shown in FIG. 42, the preamble transmits L1 blocks forevery 7.61 MHz.

For the preamble, frequency or time interleaving is performed within L1blocks and not performed between L1 blocks. That is, for the preamble,it can be said that interleaving is performed at L1 block level. Thisallows decoding the L1 blocks by transmitting L1 blocks within a tunerwindow bandwidth even when the tuner window has moved to a randomlocation within a channel bonding system.

For decoding data symbol at a random tuner window bandwidth,interleaving between data slices should not occur. That is, for dataslices, it can be said that interleaving is performed at data slicelevel. Consequently, frequency interleaving and time interleaving shouldbe performed within a data slice. Therefore, a symbol interleaver 308 ina data path of a BICM module of transmitter as shown in FIG. 4 canperform symbol interleaving for each data slice. A symbol interleaver308-1 in an L1 signal path can perform symbol interleaving for each L1block.

A frequency interleaver 403 shown in FIG. 9 needs to performinterleaving on the preamble and data symbols separately. Specifically,for the preamble, frequency interleaving can be performed for each L1block and for data symbol, frequency interleaving can be performed foreach data slice. At this point, time interleaving in data path or L1signal path may not be performed considering low latency mode.

FIG. 43 is a table analyzing overhead of L1 signaling which istransmitted in a FECFRAME header at the ModCod Header Insert (307) onthe data path of the BICM module as shown in FIG. 37. As seen in FIG.76, for short LDPC block (size=16200), a maximum overhead of 3.3% canoccur which may not be negligible. In the analysis, 45 symbols areassumed for FECFRAME protection and the preamble is a C2 frame specificL1 signaling and FECFRAME header is FECFRAME specific L1 signaling i.e.,Mod, Cod, and PLP identifier.

To reduce L1 overhead, approaches according to two Data-slice types canbe considered. For ACM/VCM type and multiple PLP casez, frame can bekept same as for the FECFRAME header. For ACM/VCM type and single PLPcases, the PLP identifier can be removed from the FECFRAME header,resulting in up to 1.8% overhead reduction. For CCM type and multiplePLP cases, the Mod/Cod field can be removed from the FECFRAME header,resulting in up to 1.5% overhead reduction. For CCM type and single PLPcases, no FECFRAME header is required, thus, up to 3.3% of overheadreduction can be obtained.

In a shortened L1 signaling, either Mod/Cod (7 bits) or PLP identifier(8 bits) can be transmitted, but it can be too short to get any codinggain. However, it is possible not to require synchronization becausePLPs can be aligned with the C2 transmission frame; every ModCod of eachPLP can be known from the preamble; and a simple calculation can enablesynchronization with the specific FECFRAME.

FIG. 44 is showing a structure for a FECFRAME header for minimizing theoverhead. In FIG. 44, the blocks with tilted lines and the FECFRAMEBuilder represent a detail block diagram of the ModCod Header Insertingmodule 307 on data path of the BICM module as shown in FIG. 4. The solidblocks represent an example of inner coding module 303, innerinterleaver 304, bit demux 305, and symbol mapper 306 on the data pathof the BICM module as shown in FIG. 4. At this point, shortened L1signaling can be performed because CCM does not require a Mod/Cod fieldand single PLP does not require a PLP identifier. On this L1 signal witha reduced number of bits, the LI signal can be repeated three times inthe preamble and BPSK modulation can be performed, thus, a very robustsignaling is possible. Finally, the ModCod Header Inserting module 307can insert the generated header into each FEC frame. FIG. 51 is showingan example of the ModCod extractor r307 on the data path of BICM demodmodule shown in FIG. 31.

As shown in FIG. 51, the FECFRAME header can be parsed at the parserr301 b, then symbols which transmit identical information in repeatedsymbols can be delayed, aligned, and then combined at Rake combiningmodule r302 b. Finally, when BPSK demodulation is performed at moduler303 b, received L1 signal field can be restored and this restored L1signal field can be sent to the system controller to be used asparameters for decoding. Parsed FECFRAME can be sent to the symboldemapper.

FIG. 45 is showing a bit error rate (BER) performance of theaforementioned L1 protection. It can be seen that about 4.8 dB of SNRgain is obtained through a three time repetition. Required SNR is 8.7 dBat BER=1E-11.

FIG. 46 is showing examples of transmission frame and FEC framestructures. The FEC frame structures shown on the upper right side ofFIG. 46 represent FECFRAME header inserted by the ModCod HeaderInserting module 307 in FIG. 4. It can be seen that depending on variouscombinations of conditions i.e., CCM or ACM/VCM type and single ormultiple PLP, different size of headers can be inserted. Or, no headercan be inserted. Transmission frames formed according to data slicetypes and shown on the lower left side of FIG. 46 can be formed by theFrame header inserting module 401 of the Frame builder as shown in FIG.9 and the merger/slicer 208 of the input processor shown in FIG. 2. Atthis point, the FECFRAME can be transmitted according to different typesof data slice. Using this method, a maximum of 3.3% of overhead can bereduced. In the upper right side of the FIG. 79, four different types ofstructures are shown, but a skilled person in the art would understandthat these are only examples, and any of these types or theircombinations can be used for the data slice.

At the receiver side, the Frame header remover r401 of the Frame parsermodule as shown in FIG. 30 and the ModCod extractor r307 of the BICMdemod module shown in FIG. 31 can extract a ModCod field parameter whichis required for decoding. At this point, according to the data slicetypes of transmission frame parameters can be extracted. For example,for CCM type, parameters can be extracted from L1 signaling which istransmitted in the preamble and for ACM/VCM type, parameters can beextracted from the FECFRAME header.

As shown in the upper right side of FIG. 79, the fecframe structure canbe divided into two groups, in which the first group is the upper threeframe structures with header and the second group is the last framestructure without header.

FIG. 47 is showing an example of L1 signaling which can be transmittedwithin the preamble by the Frame header inserting module 401 of theFrame builder module shown in FIG. 42. This L1 signaling is differentfrom the previous L1 signaling in that L1 block size can be transmittedin bits (L1_size, 14 bits); turning on/off time interleaving on dataslice is possible (dslice_time_intrlv, 1 bit); and by defining dataslice type (dslice_type, 1 bit), L1 signaling overhead is reduced. Atthis point, when the data slice type is CCM, the Mod/Cod field can betransmitted within the preamble rather than within the FECFRAME header(plp_mod (3 bits), plp_fec_type (1 bit), plp_cod (3 bits)).

At the receiver side, the shortened/punctured inner decoding moduler303-1 of the BICM demod as shown in FIG. 31 can obtain the first LDPCblock, which has a fixed L1 block size, transmitted within the preamble,through decoding. The numbers and size of the rest of the LDPC blockscan also be obtained.

Time interleaving can be used when multiple OFDM symbols are needed forL1 transmission or when there is a time-interleaved data slice. Aflexible on/off of the time interleaving is possible with aninterleaving flag. For preamble time interleaving, a time interleavingflag (1 bit) and a number of OFDM symbols interleaved (3 bits) may berequired, thus, a total of 4 bits can be protected by a way similar to ashortened FECFRAME header.

FIG. 48 is showing an example of L1-pre signaling that can be performedat the ModCod Header Inserting module 307-1 on the data path of BICMmodule shown in FIG. 4. The blocks with tilted lines and PreambleBuilder are examples of the ModCod Header Inserting module 307-1 on theL1 signaling path of the BICM module shown in FIG. 4. The solid blocksare examples of the Frame header inserting module 401 of the Framebuilder as shown in FIG. 42.

Also, the solid blocks can be examples of shortened/punctured innercoding module 303-1, inner interleaver 304-1, bit demux 305-1, andsymbol mapper 306-1 on L1 signaling path of BICM module shown in FIG. 4.

As seen in FIG. 48, the L1 signal that is transmitted in the preamblecan be protected using shortened/punctured LDPC encoding. Relatedparameters can be inserted into the Header in a form of L1-presignaling. At this point, only time interleaving parameters can betransmitted in the Header of the preamble. To ensure more robustness, afour times repetition can be performed. At the receiver side, to be ableto decode the L1 signal that is transmitted in the preamble, the ModCodextractor r307-1 on the L1 signaling path of BICM demod as shown in FIG.31 needs to use the decoding module shown in FIG. 18. At this point,because there is a four times repetition unlike the previous decodingFECFRAME header, a Rake receiving process which synchronizes the fourtimes repeated symbols and adding the symbols, is required.

FIG. 49 shows a structure of L1 the signaling block that is transmittedfrom the Frame header inserting module 401 of the Frame builder moduleas shown in FIG. 42. It is showing a case where no time interleaving isused in a preamble. As shown in FIG. 49, different kind of LDPC blockscan be transmitted in the order of the carriers. Once an OFDM symbol isformed and transmitted then a following OFDM symbol is formed andtransmitted. For the last OFDM symbol to be transmitted, if there is anycarrier left, that carriers can be used for data transmission or can bedummy padded. The example in FIG. 49 shows a preamble that comprisesthree OFDM symbol. At a receiver side, for this non-interleaving case,the symbol deinterleaver r308-1 on the L1 signaling path of BICM demodas shown in FIG. 31 can be skipped.

FIG. 50 shows a case where L1 time interleaving is performed. As shownin FIG. 50, block interleaving can be performed in a fashion of formingan OFDM symbol for identical carrier indices then forming an OFDMsymbols for the next carrier indices. As in the case where nointerleaving is performed, if there is any carrier left, that carrierscan be used for data transmission or can be dummy padded. At a receiverside, for this non-interleaving case, the symbol deinterleaver r308-1 onthe L1 signaling path of the BICM demod shown in FIG. 31 can performblock deinterleaving by reading LDPC blocks in increasing order ofnumbers of the LDPC blocks.

In addition, there can be at least two types of data slices. Data slicetype 1 has dslice_type=0 in L1 signaling fields. This type of data slicehas no XFECFrame header and has its mod/cod values in L1 signalingfields. Data slice type 2 has dslice_type=1 in L1 signaling fields. Thistype of data slice has XFECFrame header and has its mod/cod values inXFECFrame header.

XFECFrame means XFEC(compleX Forward Error Correction)Frame and mod/codmeans modulation type/coderate.

At a receiver, a frame parser can form a frame from demodulated signals.The frame has data symbols and the data symbols can have a first type ofdata slice which has an XFECFrame and an XFECFrame header and a secondtype of data slice which has XFECFrame without XFECFrame header. Also, areceiver can extract a field for indicating whether to perform timede-interleaving on the preamble symbols or not to perform timede-interleaving on the preamble symbols, from the L1 of the preamblesymbols.

At a transmitter, a frame builder can build a frame. Data symbols of theframe comprise a first type of data slice which has an XFECFrame and anXFECFrame header and a second type of data slice which has XFECFramewithout XFECFrame header. In addition, a field for indicating whether toperform time interleaving on preamble symbols or not to perform timeinterleaving on preamble symbols can be inserted in L1 of the preamblesymbols.

Lastly, for shortened/punctured code for the Frame header insertingmodule 401 of the Frame builder shown in FIG. 9, a minimum size ofcodeword that can obtain coding gain can be determined and can betransmitted in a first LDPC block. In this manner, for the rest of LDPCblock sizes can be obtained from that transmitted L1 block size.

FIG. 52 is showing another example of L1-pre signaling that can betransmitted from ModCod Header Inserting module 307-1 on L1 signalingpath of BICM module shown in FIG. 4. FIG. 52 is different from FIG. 48in that Header part protection mechanism has been modified. As seen inFIG. 52, L1 block size information L1 size (14 bits) is not transmittedin L1 block, but transmitted in Header. In the Header, time interleavinginformation of 4 bits can be transmitted too. For total of 18 bits ofinput, BCH (45, 18) code which outputs 45 bits are used and copied tothe two paths and finally, QPSK mapped. For the Q-path, 1 bit cyclicshift can be performed for diversity gain and PRBS modulation accordingto sync word can be performed. Total of 45 QPSK symbols can be outputfrom these I/O path inputs. At this point, if time interleaving depth isset as a number of preambles that is required to transmit L1 block,L1_span (3 bits) that indicates time interleaving depth may not need tobe transmitted. In other words, only time interleaving on/off flag (1bit) can be transmitted. At a receiver side, by checking only a numberof transmitted preambles, without using L1_span, time deinterleavingdepth can be obtained.

FIG. 53 is showing an example of scheduling of L1 signaling block thatis transmitted in preamble. If a size of L1 information that can betransmitted in a preamble is Nmax, when L1 size is smaller than Nmax,one preamble can transmit the information. However, when L1 size isbigger than Nmax, L1 information can be equally divided such that thedivided L1 sub-block is smaller than Nmax, then the divided L1 sub-blockcan be transmitted in a preamble. At this point, for a carrier that isnot used because of L1 information being smaller than Nmax, no data aretransmitted.

Instead, as shown in FIG. 55, power of carriers where L1 block aretransmitted can be boosted up to maintain a total preamble signal powerequal to data symbol power. Power boosting factor can be varieddepending on transmitted L1 size and a transmitter and a receiver canhave a set value of this power boosting factor. For example, if only ahalf of total carriers are used, power boosting factor can be two.

FIG. 54 is showing an example of L1-pre signaling where power boostingis considered. When compared to FIG. 52, it can be seen that power ofQPSK symbol can be boosted and sent to preamble builder.

FIG. 56 is showing another example of ModCod extractor r307-1 on L1signaling path of BICM demod module shown in FIG. 31. From inputpreamble symbol, L1 signaling FECFRAME can be output into symboldemapper and only header part can be decoded.

For input header symbol, QPSK demapping can be performed andLog-Likelihood Ratio (LLR) value can be obtained. For Q-path, PRBSdemodulation according to sync word can be performed and a reverseprocess of the 1-bit cyclic shift can be performed for restoration.

These aligned two I/O path values can be combined and SNR gain can beobtained. Output of hard decision can be input into BCH decoder. The BCHdecoder can restore 18 bits of L1-pre from the input 45 bits.

FIG. 57 is showing a counterpart, ModCod extractor of a receiver. Whencompared to FIG. 56, power control can be performed on QPSK demapperinput symbols to restore from power level boosted by transmitter to itsoriginal value. At this point, power control can be performed byconsidering a number of carriers used for L1 signaling in a preamble andby taking an inverse of obtained power boosting factor of a transmitter.The power boosting factor sets preamble power and data symbol poweridentical to each other.

FIG. 58 is showing an example of L1-pre synchronization that can beperformed at ModCod extractor r307-1 on L1 signaling path of BICMdemodulation module shown in FIG. 31. This is a synchronizing process toobtain a start position of Header in a preamble. Input symbols can beQPSK demapped then for the output Q-path, an inverse of 1 bit cyclicshift can be performed and alignment can be performed. Two I/O pathsvalues can be multiplied and modulated values by L1-pre signaling can bedemodulated. Thus, output of multiplier can express only PRBS which is async word. When the output is correlated with a known sequence PRBS, acorrelation peak at Header can be obtained. Thus, a start position ofHeader in a preamble can be obtained. If necessary, power control whichis performed to restore original power level, as in FIG. 57, can beperformed on input of QPSK demapper.

FIG. 59 is showing another example of L1 block header field which issent to the Header Inserting module 307-1 on the L1 signaling path ofthe BICM module as shown in FIG. 4. FIG. 59 is different from FIG. 52 inthat L1_span which represents the time interleaving depth is reduced to2 bits and reserved bits are increased by 1 bit. A receiver can obtaintime interleaving parameter of L1 block from the transmitted L1_span.

FIG. 60 is showing processes of equally dividing a L1 block into as manyportions as a number of preambles then inserting a header into each ofthe divided L1 blocks and then assigning the header inserted L1 blocksinto a preamble. This can be performed when a time interleaving isperformed with a number of preambles where the number of preambles isgreater than a minimum number of preambles that is required fortransmitting L1 block. This can be performed at the L1 block on the L1signaling path of the BICM module as shown in FIG. 37. The rest of thecarriers, after transmitting L1 blocks can have cyclic repetitionpatterns instead of being zero padded.

FIG. 61 is showing an example of the Symbol Demapper r306-1 of the BICMdemodulation module as shown in FIG. 31. For a case where L1 FEC blocksare repeated as shown in FIG. 60, each starting point of L1 FEC blockscan be aligned, combined at module r301 f, and then QAM demapped at QAMdemapper r302 f to obtain diversity gain and SNR gain. At this point,the combiner can include processes of aligning and adding each L1 FECblock and dividing the added L1 FEC block. For a case where only part ofthe last FEC block is repeated as shown in FIG. 60, only the repeatedpart can be divided into as many as a number of FEC block header and theother part can be divided by a value which is one less than a number ofFEC block header. In other words, the dividing number corresponds to anumber of carriers that is added to each carrier.

FIG. 65 is showing another example of L1 block scheduling. FIG. 65 isdifferent from FIG. 60 in that, instead of performing zero padding orrepetition when L1 blocks do not fill one OFDM symbol, OFDM symbol canbe filled with parity redundancy by performing less puncturing onshortened/punctured code at the transmitter. In other words, when paritypuncturing module 304 c is performed at FIG. 5, the effective coderatecan be determined according to the puncturing ratio, thus, by puncturingas less bits have to be zero padded, the effective coderate can belowered and a better coding gain can be obtained. The Paritydepuncturing module r303 a of a receiver as shown in FIG. 32 can performdepuncturing considering the less punctured parity redundancy. At thispoint, because a receiver and a transmitter can have information of thetotal L1 block size, the puncturing ratio can be calculated.

FIG. 62 is showing another example of L1 signaling field. FIG. 62 isdifferent from FIG. 41 in that, for a case where the data slice type isCCM, a start address (21 bits) of the PLP can be transmitted. This canenable FECFRAME of each PLP to form a transmission frame, without theFECFRAME being aligned with a start position of a transmission frame.Thus, padding overhead, which can occur when a data slice width isnarrow, can be eliminated. A receiver, when a data slice type is CCM,can obtain ModCod information from the preamble at the L1 signaling pathof the BICM demod module as shown in FIG. 31, instead of obtaining itfrom FECFRAME header. In addition, even when a zapping occurs at arandom location of transmission frame, FECFRAME synchronization can beperformed without delay because the start address of PLP can be alreadyobtained from the preamble.

FIG. 63 is showing another example of L1 signaling fields which canreduce the PLP addressing overhead.

FIG. 64 is showing the numbers of QAM symbols that corresponds to aFECFRAME depending on the modulation types. At this point, a greatestcommon divisor of QAM symbol is 135, thus, an overhead of log 2(135)≈7bits can be reduced. Thus, FIG. 63 is different from FIG. 62 in that anumber of PLP_start field bits can be reduced from 21 bits to 14 bits.This is a result of considering 135 symbols as a single group andaddressing the group. A receiver can obtain an OFDM carrier index wherethe PLP starts in a transmission frame after obtaining the PLP_startfield value and multiplying it by 135.

FIG. 66 and FIG. 68 show examples of symbol interleaver 308 which cantime interleave data symbols which are sent from the ModCod HeaderInserting module 307 on the data path of BICM module as shown in FIG. 4.

FIG. 66 is an example of Block interleaver for time interleaving whichcan operate on a data-slice basis. The row value means a number ofpayload cells in four of the OFDM symbols within one data-slice.Interleaving on OFDM symbol basis may not be possible because the numberof cells may change between adjacent OFDM cells. The column value Kmeans a time interleaving depth, which can be 1, 2, 4, 8, or 16 . . .Signaling of K for each data-slice can be performed within the L1signaling. Frequency interleaver 403 as shown in FIG. 9 can be performedprior to time interleaver 308 as shown in FIG. 4.

FIG. 67 shows an interleaving performance of the time interleaver asshown in FIG. 66. It is assumed that a column value is 2, a row value is8, a data-slice width is 12 data cells, and that no continual pilots arein the data-slice. The top figure in FIG. 67 is an OFDM symbol structurewhen time interleaving is not performed and the bottom figure is an OFDMsymbol structure when time interleaving is performed. The black cellsrepresent scattered pilot and the non-black cells represent data cells.The same kind of data cells represents an OFDM symbol. In FIG. 100, datacells that correspond to a single OFDM symbol are interleaved into twosymbols. An interleaving memory that corresponds to eight OFDM symbolsis used but the interleaving depth corresponds to only two OFDM symbols,thus, full interleaving depth is not obtained.

FIG. 68 is suggested for achieving full interleaving depth. In FIG. 68,the black cells represent scattered pilots and the non-black cellsrepresent data cells. Time interleaver as shown in FIG. 68 can beimplemented in a form of block interleaver and can interleavedata-slices. In FIG. 68, a number of column, K represents a data-slicewidth, a number of row, N represents time interleaving depth and thevalue, K can be random values i.e., K=1, 2, 3, . . . . The interleavingprocess includes writing data cell in a column twist fashion and readingin a column direction, excluding pilot positions. That is, it can besaid that the interleaving is performed in a row-column twisted fashion.

In addition, at a transmitter, the cells which are read in a columntwisted fashion of the interleaving memory correspond to a single OFDMsymbol and the pilot positions of the OFDM symbols can be maintainedwhile interleaving the cells.

Also, at a receiver, the cells which are read in a column twistedfashion of the de-interleaving memory correspond to a single OFDM symboland the pilot positions of the OFDM symbols can be maintained while timede-interleaving the cells.

FIG. 69 shows time interleaving performance of FIG. 68. For comparisonwith FIG. 66, it is assumed that a number of row is 8, a data-slicewidth is 12 data cells, and that no continual pilots are in thedata-slice. In FIG. 69, data cells correspond to a single OFDM symbolare interleaved into eight OFDM symbols. As shown in FIG. 102, aninterleaving memory that corresponds to eight OFDM symbols is used andthe resulting interleaving depth corresponds to eight OFDM symbols,thus, full interleaving depth is obtained.

The time interleaver as shown in FIG. 68 can be advantageous in thatfull interleaving depth can be obtained using identical memory;interleaving depth can be flexible, as opposed to FIG. 66; consequently,a length of transmission frame can be flexible too, i.e., rows need notbe multiples of four. Additionally, the time interleaver used for dataslice, can be identical to the interleaving method used for the preambleand also can have commonality with a digital transmission system whichuses general OFDM. Specifically, the time interleaver 308 as shown inFIG. 4 can be used before the frequency interleaver 403 as shown in FIG.9 is used. Regarding a receiver complexity, no additional memory can berequired other than additional address control logic which can requirevery small complexity.

FIG. 70 shows a corresponding symbol deinterleaver (r308) in a receiver.It can perform deinterleaving after receiving output from the FrameHeader Remover r401. In the deinterleaving processes, compared to FIG.66, the writing and reading processes of block interleaving areinverted. By using pilot position information, time deinterleaver canperform virtual deinterleaving by not writing to or reading from a pilotposition in the interleaver memory and by writing to or reading from adata cell position in the interleaver memory. Deinterleaved informationcan be output into the ModCod Extractor r307.

FIG. 71 shows another example of time interleaving. Writing in diagonaldirection and reading row-by-row can be performed. As in FIG. 68,interleaving is performed taking into account the pilot positions.Reading and writing is not performed for pilot positions butinterleaving memory is accessed by considering only data cell positions.

FIG. 72 shows a result of interleaving using the method shown in FIG.71. When compared to FIG. 69, cells with the same patterns are dispersednot only in time domain, but also in the frequency domain. In otherwords, full interleaving depth can be obtained in both time andfrequency domains.

FIG. 75 shows a symbol deinterleaver r308 of a corresponding receiver.The output of Frame Header Remover r401 can be deinterleaved. Whencompared to FIG. 66, deinterleaving has switched the order of readingand writing. Time deinterleaver can use pilot position information toperform virtual deinterleaving such that no reading or writing isperformed on pilot positions but so that reading or writing can beperformed only on data cell positions. Deinterleaved data can be outputinto the ModCod Extractor r307.

FIG. 73 shows an example of the addressing method of FIG. 72. NT meanstime interleaving depth and ND means data slice width. It is assumedthat a row value, N is 8, a data-slice width is 12 data cells, and nocontinual pilots are in data-slice. FIG. 73 represents a method ofgenerating addresses for writing data on a time interleaving memory,when a transmitter performs time interleaving. Addressing starts from afirst address with Row Address (RA)=0 and Column Address (CA)=0. At eachoccurrence of addressing, RA and CA are incremented. For RA, a modulooperation with the OFDM symbols used in time interleaver can beperformed. For CA, a modulo operation with a number of carriers thatcorresponds to a data slice width can be performed. RA can beincremented by 1 when carriers that correspond to a data slice arewritten on a memory. Writing on a memory can be performed only when acurrent address location is not a location of a pilot. If the currentaddress location is a location of a pilot, only the address value can beincreased.

In FIG. 73, a number of column, K represents the data-slice width, anumber of row, N represents the time interleaving depth and the value, Kcan be a random values i.e., K=1, 2, 3, . . . . The interleaving processcan include writing data cells in a column twist fashion and reading incolumn direction, excluding pilot positions. In other words, virtualinterleaving memory can include pilot positions but pilot positions canbe excluded in actual interleaving.

FIG. 76 shows deinterleaving, an inverse process of time interleaving asshown in FIG. 71. Writing row-by-row and reading in diagonal directioncan restore cells in original sequences.

The addressing method used in a transmitter can be used in a receiver.Receiver can write received data on a time deinterleaver memoryrow-by-row and can read the written data using generated address valuesand pilot location information which can be generated in a similarmanner with that of a transmitter. As an alternative manner, generatedaddress values and pilot information that were used for writing can beused for reading row-by-row.

These methods can be applied in a preamble that transmits L1. Becauseeach OFDM symbol which comprises preamble can have pilots in identicallocations, either interleaving referring to address values taking intoaccount the pilot locations or interleaving referring to address valueswithout taking into account the pilot locations can be performed. Forthe case of referring to address values without taking into account thepilot locations, the transmitter stores data in a time interleavingmemory each time. For such a case, a size of memory required to performinterleaving/deinterleaving preambles at a receiver or a transmitterbecomes identical to a number of payload cells existing in the OFDMsymbols used for time interleaving.

FIG. 74 is another example of L1 time interleaving. In this example,time interleaving can place carriers to all OFDM symbols while thecarriers would all be located in a single OFDM symbol if no timeinterleaving was performed. For example, for data located in a firstOFDM symbol, the first carrier of the first OFDM symbol will be locatedin its original location. The second carrier of the first OFDM symbolwill be located in a second carrier index of the second OFDM symbol. Inother words, i-th data carrier that is located in n-th OFDM symbol willbe located in an i-th carrier index of (i+n) mod N th OFDM symbol, wherei=0, 1, 2 . . . number of carrier−1, n=0, 1, 2 . . . , N−1, and N is anumber of OFDM symbols used in L1 time interleaving. In this L1 timeinterleaving method, it can be said that interleaving for all the OFDMsymbols are performed a twisted fashion as shown in FIG. 107. Eventhough pilot positions are not illustrated in FIG. 107, as mentionedabove, interleaving can be applied to all the OFDM symbols includingpilot symbols. That is, it can be said that interleaving can beperformed for all the OFDM symbols without considering pilot positionsor regardless of whether the OFDM symbols are pilot symbols or not.

If a size of a LDPC block used in L1 is smaller than a size of a singleOFDM symbol, the remaining carriers can have copies of parts of the LDPCblock or can be zero padded. At this point, a same time interleaving asabove can be performed. Similarly, in FIG. 74, a receiver can performdeinterleaving by storing all the blocks used in L1 time interleaving ina memory and by reading the blocks in the order in which they have beeninterleaved, i.e., in order of numbers written in blocks shown in FIG.74.

When a block interleaver as shown in FIG. 73 is used, two buffers areused. Specifically, while one buffer is storing input symbols,previously input symbols can be read from the other buffer. Once theseprocesses are performed for one symbol interleaving block,deinterleaving can be performed by switching order of reading andwriting, to avoid memory access conflict. This “ping-pong” styledeinterleaving can have a simple address generation logic. However,hardware complexity can be increased when using two symbol interleavingbuffers.

FIG. 77 shows an example of a symbol deinterleaver r308 or r308-1 asshown in FIG. 31. This proposed embodiment of the invention can use onlya single buffer to perform deinterleaving. Once an address value isgenerated by the address generation logic, the address value can beoutput from the buffer memory and in-placement operation can beperformed by storing a symbol that is input into the same address. Bythese processes, a memory access conflict can be avoided while readingand writing. In addition, symbol deinterleaving can be performed usingonly a single buffer. Parameters can be defined to explain this addressgeneration rule. As shown in FIG. 73, a number of rows of adeinterleaving memory can be defined as time interleaving depth, D and anumber of columns of the deinterleaving memory can be defined as dataslice width, W. Then the address generator can generate the followingaddresses.

i-th sample on j-th block, including pilot

i=0, 1, 2, . . . , N−1;

N=D*W;

Ci,j=i mod W;

Tw=((Ci,j mod D)*j) mod D;

Ri,j=((i div W)+Tw) mod D;

Li,j(1)=Ri,j*W+Ci,j;

Or

Li,j(2)=Ci,j*D+Ri,j;

The addresses include pilot positions, thus, input symbols are assumedto include pilot positions. If input symbols that include only datasymbols need to be processed, additional control logic which skips thecorresponding addresses can be required. At this point, i represents aninput symbol index, j represents an input interleaving block index, andN=D*W represents an interleaving block length. Mod operation representsmodulo operation which outputs remainder after division. Div operationrepresents division operation which outputs quotient after division.Ri,j and Ci,j represent row address and column address of i-th symbolinput of j-th interleaving block, respectively. Tw represents columntwisting value for addresses where symbols are located. In other words,each column can be considered as a buffer where independent twisting isperformed according to Tw values. Li,j represents an address when singlebuffer is implemented in an one dimension sequential memory, not in twodimension. Li,j can have values from 0 to (N−1). Two different methodsare possible. Li,j(1) is used when the memory matrix is connectedrow-by-row and Li,j(2) is used when the memory matrix is connected incolumn-by-column.

FIG. 78 shows an example of row and column addresses for timedeinterleaving when D is 8 and W is 12. J starts from j=0 and for each jvalue, a first row can represent the row address and a second row canrepresent the column address. FIG. 78 shows only addresses of the first24 symbols. Each column index can be identical to the input symbol indexi.

FIG. 80 shows an example of an OFDM transmitter using a data slice. Asshown in FIG. 80, the transmitter can comprise a data PLP path, an L1signaling path, a frame builder, and an OFDM modulation part. The dataPLP path is indicated by blocks with horizontal lines and verticallines. The L1 signaling path is indicated by blocks with tilted lines.Input processing modules 701-0, 701-N, 701-K, and 701-M can compriseblocks and sequences of input interface module 202-1, input streamsynchronizer 203-1, delay compensator 204-1, null packet deleting module205-1, CRC encoder 206-1, BB header inserting module 207-1, and BBscrambler 209 performed for each PLP as shown in FIG. 2. FEC modules702-0, 702-N, 702-K, and 702-M can comprise blocks and sequences ofouter coding module 301 and inner coding module 303 as shown in FIG. 4.An FEC module 702-L1 used on the L1 path can comprise blocks andsequences of outer coding module 301-1 and shortened/punctured innercoding module 303-1 as shown in FIG. 4. L1 signal module 700-L1 cangenerate L1 information required to comprise a frame.

Bit interleaving modules 703-0, 703-N, 703-K, and 703-M can compriseblocks and sequences of inner interleaver 304 and bit demux 305 as shownin FIG. 37. Bit interleaving module 703-L1 used on the L1 path cancomprise blocks and sequences of inner interleaving module 304-1 and bitdemux 305-1 as shown in FIG. 4. Symbol mapper modules 704-0, 704-N,704-K, and 704-M can perform functions identical with the functions ofthe symbol mapper 306 shown in FIG. 4. The symbol mapper module 704-L1used on L1 path can perform functions identical with the functions ofthe symbol mapper 306-1 shown in FIG. 4. FEC header modules 705-0,705-N, 705-K, and 705-M can perform functions identical with thefunctions of the ModCod Header inserting module 307 shown in FIG. 4. FECheader module 705-L1 for the L1 path can perform functions identicalwith the functions of the ModCod Header inserting module 307-1 shown inFIG. 4.

Data slice mapper modules 706-0 and 706-K can schedule FEC blocks tocorresponding data slices and can transmit the scheduled FEC blocks,where the FEC blocks correspond to PLPs that are assigned to each dataslice. Preamble mapper 707-L1 can schedule L1 signaling FEC blocks topreambles. L1 signaling FEC blocks are transmitted in preambles. Timeinterleaver modules 708-0 and 708-K can perform functions identical withthe functions of the symbol interleaver 308 shown in FIG. 4 which caninterleave data slices. Time interleaver 708-L1 used on L1 path canperform functions identical with the functions of the symbol interleaver308-1 shown in FIG. 4.

Alternatively, time interleaver 708-L1 used on L1 path can performidentical functions with symbol interleaver 308-1 shown in FIG. 3, butonly on preamble symbols.

Frequency interleaver blocks 709-0 and 709-K can perform frequencyinterleaving on data slices. Frequency interleaver 709-L1 used on L1path can perform frequency interleaving according to preamble bandwidth.

Pilot generating module 710 can generate pilots that are suitable forcontinuous pilot (CP), scattered pilot (SP), data slice edge, andpreamble. A frame can be built from scheduling the data slice, preamble,and pilot at module 711. The IFFT module 712 and GI inserting module 713can perform functions identical with the functions of the IFFT module501 and the GI inserting module 503 blocks shown in FIG. 18,respectively. Lastly, DAC 714 can convert digital signals into analogsignals and the converted signals can be transmitted.

FIG. 81 shows an example of an OFDM receiver which uses data slice. InFIG. 81, tuner r700 can perform the functions of the tuner/AGC r603 andthe functions of the down converter r602 shown in FIG. 61. ADC r701 canconvert received analog signals into digital signals. Time/freqsynchronizer r702 can perform functions identical with the functions ofthe time/freq synchronizer r505 shown in FIG. 62. Frame detector r703can perform functions identical with the functions of the frame detectorr506 shown in FIG. 62.

At this point, after time/frequency synchronization are performed,synchronization can be improved by using preamble in each frame that issent from frame detector r703 during tracking process.

GI remover r704 and FFT module r705 can perform functions identical withthe functions of the GI remover r503 and the FFT module r502 shown inFIG. 62, respectively.

Channel estimator r706 and channel EQ r707 can perform a channelestimation part and a channel equalization part of the channel Est/Eqr501 as shown in FIG. 62. Frame parser r708 can output a data slice andpreamble where services selected by a user are transmitted. Blocksindicated by tilted lines process a preamble. Blocks indicated byhorizontal lines which can include common PLP, process data slices.Frequency deinterleaver r709-L1 used on the L1 path can performfrequency deinterleaving within the preamble bandwidth. Frequencydeinterleaver r709 used on the data slice path can perform frequencydeinterleaving within data slice. FEC header decoding module r712-L1,time deinterleaver r710-L1, and symbol demapper r713-L1 used on the L1path can perform functions identical with the functions of the ModCodextractor r307-1, symbol deinterleaver r308-1, and symbol demapperr306-1 shown in FIG. 31.

Bit deinterleaver r714-L1 can comprise modules and sequences of bitdemux r305-1 and inner deinterleaver r304-1 as shown in FIG. 31. FECdecoding module r715-L1 can comprise modules and sequences ofshortened/punctured inner coding module r303-1 and outer decoding moduler301-1 shown in FIG. 31. At this point, the output of the L1 path can beL1 signaling information and can be sent to a system controller forrestoring PLP data that are transmitted in data slices.

Time deinterleaver r710 used on the data slice path can performfunctions identical with the functions of the symbol deinterleaver r308shown in FIG. 31. Data slice parser r711 can output user selected PLPfrom the data slices and, if necessary, common PLP associated with theuser selected PLP. FEC header decoding module r712-C and r712-K canperform functions identical with the functions of the ModCod extractorr307 shown in FIG. 31. Symbol demapper r713-C and r713-K can performfunctions identical with the functions of the symbol demapper r306 shownin FIG. 31.

Bit deinterleaver r714-C and r714-K can comprise blocks and sequences ofbit demux r305 and inner deinterleaver r304 as shown in FIG. 31. FECdecoding module r715-C and r715-K can comprise blocks and sequences ofinner decoding module r303 and outer decoding module r301 as shown inFIG. 31. Lastly, output processor r716-C and r716-K can comprise blocksand sequences of BB descrambler r209, BB header remover r207-1, CRCdecoder r206-1, null packet inserting module r205-1, delay recoverr204-1, output clock recovering module r203-1, and output interfacemodule r202-1 which are performed for each PLP in FIG. 2. If a commonPLP is used, the common PLP and data PLP associated with the common PLPcan be transmitted to a TS recombiner and can be transformed into a userselected PLP.

It should be noted from FIG. 81, that in a receiver, the blocks on theL1 path are not symmetrically sequenced to a transmitter as opposed tothe data path where the blocks are symmetrically positioned or inopposite sequence of a transmitter. In other words, for the data path,Frequency deinterleaver r709, Time deinterleaver r710, Data slice parserr711, and FEC header decoding module r712-C and r712-K are positioned.However, for the L1 path, Frequency deinterleaver r709-L1, FEC headerdecoding module r712-L1, and time deinterleaver r710-L1 are positioned.

FIG. 79 shows an example of general block interleaving in a data symboldomain where pilots are not used. As seen from the left figure,interleaving memory can be filled without black pilots. To form arectangular memory, padding cells can be used if necessary. In the leftfigure, padding cells are indicated as cells with tilted lines. In theexample, because one continual pilot can overlap with one kind ofscattered pilot pattern, a total of three padding cells are requiredduring four of OFDM symbol duration. Finally, n the middle figure,interleaved memory contents are shown.

As in the left figure of FIG. 79, either writing row-by-row andperforming column twisting; or writing in a twisted fashion from thebeginning, can be performed. Output of the interleaver can comprisereading row-by-row from memory. The output data that has been read canbe placed as shown in the right figure when OFDM transmission isconsidered. At this time, for simplicity, frequency interleaving can beignored. As seen in the figure, frequency diversity is not as high asthat of FIG. 73, but is maintained at a similar level. Most of all, itcan be advantageous in that the memory required to perform interleavingand deinterleaving can be optimized. In the example, memory size can bereduced from W*D to (W−1)*D. As the data slice width becomes bigger, thememory size can be further reduced.

For time deinterleaver inputs, a receiver should restore memory buffercontents in a form of the middle figure while considering padding cells.Basically, OFDM symbols can be read symbol-by-symbol and can be savedrow-by-row. De-twisting corresponding to column twisting can then beperformed. The output of the deinterleaver can be output in a form ofreading row-by-row from the memory of the left figure. In this fashion,when compared to the method shown in FIG. 73, pilot overhead can beminimized, and consequently interleaving/deinterleaving memory can beminimized.

FIG. 82 shows an example of a time interleaver 708-L1 for L1 path ofFIG. 80. As shown in the FIG. 82, time interleaving for the preamblewhere L1 is transmitted, can include interleaving L1 data cells,excluding pilots that are usually transmitted in the preamble. Theinterleaving method can include writing input data in a diagonaldirection (solid lines) and reading the data row-by-row (dotted lines),using identical to methods which are shown in reference to FIG. 73.

FIG. 82 shows an example of a time deinterleaver r712-L1 on the L1 pathas shown in FIG. 81. As shown in FIG. 82, for a preamble where L1 istransmitted, deinterleaving L1 data cell can be performed, excluding thepilots that are regularly transmitted in the preamble. Thedeinterleaving method can be identical to the method as shown in FIG. 76where input data are written row-by-row (solid lines) and read in adiagonal direction (dotted lines). The input data does not include anypilot, consequently, the output data has L1 data cells that do notinclude pilot either. When a receiver uses a single buffer in a timedeinterleaver for the preamble, the address generator structure that hasa deinterleaver memory as shown in FIG. 77 can be used.

Deinterleaving r712-L1 can be performed using address operations asfollows:

i-th sample on j-th block, including pilot

i=0, 1, 2, . . . , N−1;

N=D*W;

Ci,j=i mod W;

Tw=((Ci,j mod D)*j) mod D;

Ri,j=((i div W)+Tw) mod D;

Li,j(1)=Ri,j*W+Ci,j;

Or

Li,j(2)=Ci,j*D+Ri,j;

In the above operations, a length of a row, W is a length of a row of aninterleaving memory as shown in FIG. 82. Column length, D is a preambletime interleaving depth, which is a number of OFDM symbols that arerequired for transmitting preambles.

FIG. 83 shows an example of forming OFDM symbols by scheduling pilotsand input preambles from the frame builder 711 as shown in FIG. 80.Blank cells form a L1 header which is an output signal of the FEC header705-L1 on the L1 path, as shown in FIG. 80. Grey cells representcontinual pilots for the preamble which are generated by the pilotgenerating module 710 as shown in FIG. 80. Cells with patterns representthe L1 signaling cells which are an output signal of the preamble mapper707-L1 as shown in FIG. 80. The left figure represents OFDM symbols whentime interleaving is off and the right figure represents OFDM symbolswhen time interleaving is on. L1 header can be excluded from timeinterleaving because L1 header transmits a L1 signaling field length anda time interleaving on/off flag information. It is because the L1 headeris added before time interleaving. As aforementioned, time interleavingis performed excluding pilot cells. The remaining of L1 data cells canbe interleaved as shown in FIG. 82, then can be assigned to OFDMsubcarriers.

FIG. 84 shows an example of a Time Interleavers 708-0˜708-K that caninterleave data symbols that are sent from Data Slice Mappers706-0˜706-K on data path of an OFDM transmitter using data slice shownin FIG. 80. Time interleaving can be performed for each data slice. Timeinterleaved symbols can be output into Frequency Interleavers709-0˜709-K.

FIG. 84 also shows an example of a simple time interleaver using asingle buffer. FIG. 84( a) shows a structure of OFDM symbols before Timeinterleaving. Blocks with same patterns represent same kind of OFDMsymbols. FIGS. 84( b) and 84(b) show a structure of OFDM symbols afterTime interleaving. Time interleaving method can be divided into Type 1and Type 2. Each type can be performed alternatively for even symbolsand odd symbols. A receiver can perform deinterleaving accordingly. Oneof reasons of alternatively using type 1 and type 2 is to reduce memoryrequired at a receiver by using a single buffer during timedeinterleaving.

FIG. 84( b) shows a time interleaving using interleaving type 1. Inputsymbols can be written in downward diagonal direction and can be read ina row direction. FIG. 84( c) shows a time interleaving usinginterleaving type 2. Input symbols can be written in upward diagonaldirection and can be read in a row direction. The difference betweentype 1 and type 2 is whether a direction of writing input symbol isupward or downward. The two methods are different in a manner of writingsymbols, however the two methods are identical in terms of exhibitingfull time interleaving depth and full frequency diversity. However,using these methods can cause a problem during synchronization at areceiver because of using two interleaving schemes.

There can be two possible solutions. First solution can be signaling 1bit of an interleaving type of a first interleaver block that comesfirst after each preamble, through L1 signaling of preamble. This methodis performing a correct interleaving through signaling. Second solutioncan be forming a frame to have a length of an even number ofinterleaving blocks. Using this method, a first interleaving block ofeach frame can have an identical type, thus, interleaving blocksynchronization problem can be resolved. For example, synchronizationissue can be resolved by applying type 1 interleaving to a firstinterleaving block and sequentially applying to next interleaving blockswithin each frame, then ending a last interleaving block of each framewith type 2 interleaving. This method requires a frame to be composed oftwo interleaving blocks but can be advantageous in that no additionalsignaling is required as in the first method.

FIG. 89 shows a structure of a Time deinterleaver r710 of a receivershown in FIG. 81. Time De-interleaving can be performed on outputs ofFrequency deinterleaver r709. Time de-interleaver of FIG. 89 representsa de-interleaving scheme which is an inverse process of a timeinterleaving shown in FIG. 84. The de-interleaving, compared to FIG. 84,will have an opposite manner in reading and writing. In other words,type 1 deinterleaver can write input symbols in a row direction and canread the written symbols in downward diagonal direction. Type 2deinterleaver can write input symbols in downward diagonal direction andcan read the written symbols in a row direction. These methods canenable writing received symbols where symbols are previously read bymaking a direction of writing symbols of type 2 deinterleaver identicalto a direction of reading symbols of type 1 deinterleaver. Thus, areceiver can perform deinterleaving using a single buffer. In addition,a simple implementation can be realized because of deinterleavingmethods of type 1 and type 2 are performed by either writing and readingsymbols in a diagonal direction or in a row direction.

However, using these methods can cause a problem in synchronization at areceiver because of using two interleaving schemes. For example,de-interleaving type 1 interleaved symbols in a type 2 manner can causedeterioration in performance. There can be two possible solutions. Firstsolution can be determining a type of an interleaving block that comesafter a preamble, using 1 bit of an interleaving type of a transmittedL1 signaling part. Second solution can be performing deinterleavingusing a type according to a first interleaving block within a frame, ifa number of interleaving blocks within a frame is even number.De-interleaved symbol can be output into Data Slice Parser r711.

FIG. 85 shows an address generation logic that is identical with anaddress generation logic of a single buffer, when a block interleaveruses two memory buffers as in FIG. 73. The address generation logic canperform identical functions as functions shown in FIG. 73. By defining atime interleaving depth D as a number of rows of a deinterleaving memoryand defining a data slice width W as a number of column, addresses shownin the FIG. 85 can be generated by an address generator. The addressescan include pilot positions. To time interleave input symbols thatinclude only data symbols, a control logic that can skip addresses maybe required. Addresses used in interleaving preambles may not requirepilot positions and interleaving can be performed using L1 blocks. The irepresents an index of an input symbol, N=D*W represents an interleavingblock length. Ri and Ci represent a row address and a column address ofan i-th input symbol, respectively. Tw represents a column twistingvalue or twisting parameter from an address where a symbol is located.Li represents addresses when one dimensional memory having a singlebuffer is implemented. Values of Li can be from 0 to (N−1). In this onedimensional memory, at least two methods are possible. Li(1) is couplinga memory matrix row-by-row and Li(2) is coupling a memory matrixcolumn-by-column. A receiver can use the address generation logic inreading symbols during a de-interleaving.

FIG. 86 shows another example of a preamble. For a case when an OFDMsymbol having a size of 4K-FFT is used in 7.61 MHz bandwidth and a sixthcarrier within a OFDM symbol and carriers at both ends are used aspilots, a number of carriers that can be used in L1 signaling can beassumed to be 2840. When multiple channels are bonded, multiple preamblebandwidths can exist. The number of carriers can change depending on atype of pilots to be used, an FFT size, a number of bonded channels, andothers factors. If a size of an L1_XFEC_FRAME that includes L1_header(H) that is to be assigned to a single OFDM symbol and L1 FEC block(L1_FEC1) is smaller than a single OFDM symbol (5 w-a-1), L1_XFEC_FRAMEincluding L1_header can be repeated to fill a remaining part of thesingle OFDM symbol (5 w-a-2). This is similar to preamble structure ofFIG. 60. For a receiver to receive a data slice that is located in acertain bandwidth of bonded channels, a tuner window of the receiver canbe located in a certain bandwidth.

If a tuner window of a receiver is located as 5 w-a-3 of FIG. 86, anincorrect result can occur during merging repeated L1_XFEC_FRAMEs. Case1 of FIG. 86 can be such an example. A receiver finds L1_Header (H) tolocate a start position of a L1_Header (H) within a tuner window, butthe found L1_Header can be a header of a incomplete L1_XFEC_FRAME (5w-a-4). L1 signaling information may not be obtained correctly if alength of L1_XFEC_FRAME is obtained based on that L1_Header and a restof part (5 w-a-5) is added to a start position of that L1_Header. Toprevent such a case, a receiver may need additional operations to find aheader of a complete L1_XFEC_FRAME. FIG. 87 shows such operations. Inthe example, to find a header of a complete L1_XFEC_FRAME, if anincomplete L1_XFEC_FRAME exists in a preamble, a receiver can use atleast two L1_Headers to find a start location of L1_Header for mergingL1_XFEC_FRAME. First, a receiver can find L1_Header from a preamble OFDMsymbol (5 w-b-1). Then using a length of an L1_XFEC_FRAME within thefound L1_Header, the receiver can check if every L1_XFEC_FRAME within acurrent OFDM symbol is a complete block (5 w-b-2). If it's not, thereceiver can find another L1_Header from current preamble symbol (5w-b-3). From a calculated distance between a newly found L1_Header and aprevious L1_Header, whether a certain L1_XFEC_FRAME is a complete blockcan be determined (5 w-b-4). Then, an L1_Header of a completeL1_XFEC_FRAME can be used as a stating point for merging. Using thestating point, L1_XFEC_FRAME can be merged (5 w-b-5). Using theseprocesses, case 2 or correct merging shown in FIG. 86 can be expected ata receiver. These processes can be performed at FEC Header Decoderr712-L1 on L1 signal path of FIG. 81.

FIG. 88 is an example of a preamble structure that can eliminate theaforementioned additional operations at a receiver. As opposed to theprevious preamble structure, when a remaining part of an OFDM symbol isfilled, only L1_FEC1 of an L1_XFEC_FRAME, excluding L1_Header(H) can berepeatedly filled (5 w-c-2). In this way, when a receiver finds a startposition of a L1_Header (H) to merge L1_XFEC_FRAME, L1_Header of onlycomplete L1_XFEC_FRAME can be found (5 w-c-4), thus, without additionaloperations, L1_XFEC_FRAME can be merged using the found L1_Header.Therefore, processes such as (5 w-b-2), (5 w-b-3), and (5 w-b-4) shownin FIG. 87 can be eliminated at a receiver. These processes andcounterpart processes of the processes can be performed at FEC HeaderDecoder 712-L1 on L1 signal path of a receiver of FIG. 81 and at FECHeader 705-L1 on L1 signal path of a transmitter of FIG. 80.

Time deinterleaver r712-L1 on L1 path of a receiver of FIG. 81 cande-interleave L1 block cells or cells with patterns, excluding othercells such as preamble header and pilot cells. L1 block cells arerepresented by cells with patterns as shown in FIG. 83. FIG. 90 showsanother example of an OFDM transmitter that uses data slices. Thistransmitter can have identical structure and can perform identicalfunction with the transmitter of FIG. 80, except the added and modifiedblocks. The preamble mapper 1007-L1 can map L1 blocks and L1 blockheaders which are outputs from FEC header 705-L1 into preamble symbolsused in a transmission frame. Specifically, L1 block header can berepeated for each preamble and the L1 block can be divided as many as anumber of used preambles. Time interleaver 1008-L1 can interleave L1blocks that are divided into preambles. At this point, L1 block headercan be either included in interleaving or not included in interleaving.Whether the L1 block header is included or not may not change a signalstructure of an L1 block header but it can change an order ofinterleaving and transmitting L1 blocks. L1_XFEC repeater 1015-L1 canrepeat the time interleaved L1_XFEC blocks within a preamble bandwidth.At this point, the L1 block header can be either repeated within apreamble or not repeated within a preamble.

FIG. 91 shows another example of an OFDM receiver using data slices.This receiver has identical structure and can perform identical functionwith the receiver of FIG. 81, except the added and modified blocks. FECheader decoding module r1012-L1 can synchronize L1 headers within apreamble. If L1 headers are repeated, L1 headers can be combined toobtain an SNR gain. Then, FEC header decoding module r712-L1 of FIG. 81can perform an FEC decoding. The synchronization process can give alocation of a header by correlating sync word of a header and preambles.For frequency offsets of multiple of an integer, a correlation range canbe determined from circular addressing.

L1_XFEC combining module r1017-L1 can combine L1_XFEC blocks to obtainan SRN gain, when divided L1 blocks are received within a preamble. Timedeinterleaver r1010-L1 can time de-interleave L1 blocks within apreamble. Depending on whether L1 block headers are time interleaved ata transmitter or not, L1 block headers can be de-interleaved at areceiver accordingly. A deinterleaving order of L1 blocks can be changeddepending on whether L1 block headers are time interleaved at atransmitter or not. For example, when time interleaving is ON as in FIG.83, a location of the number 33 cell which is a first L1 block cellwithin a first preamble, can change. In other words, when L1 blockheaders are not included in an interleaving, interleaved signal havingthe locations of cells as shown in FIG. 83 will be received. If L1 blockheaders are included in an interleaving, a location of the number 33cell needs to be changed to de-interleave cells that are interleaveddiagonally, using a first cell of a first L1 block header within a firstpreamble as a reference. L1_FEC merger r1018-L1 can merge L1 blocks thatare divided into many preambles into a single L1 block for FEC decoding.

With an additional 1 bit, PLP_type field of L1 signaling fields that aretransmitted in a preamble can have following values.

PLP_type=00 (common PLP)

PLP_type=01 (normal data PLP)

PLP_type=10 (de-multiplexed data PLP)

PLP_type=11 (reserved)

A normal data PLP represents a data PLP when a single service istransmitted in a single data slice. A de-multiplexed data PLP representsa data PLP when a single service is de-multiplexed into multiple dataslices. When a user changes service, if L1 signaling and L2 signalingare stored at a receiver, waiting for an L1 signaling information withina next frame can be eliminated. Therefore, a receiver can changeservices efficiently and a user can have benefit of less delay during aservice change. FIG. 95 shows signal structures of L1 block that istransmitted in a preamble, for time interleaving flow and timede-interleaving flow. As seen in FIG. 95, interleaving anddeinterleaving can be performed not on a whole preamble bandwidth, buton a divided L1 block.

FIG. 96 is an example of an L1 time interleaving field of signalingfields of L1, processed by FEC header 705-L1 on L1 path shown in FIG.90. As shown in FIG. 96, one bit or two bits can be used for timeinterleaving parameter. If one bit is used, interleaving is notperformed when bit value is 0 and interleaving having depth of OFDMsymbols used in preamble symbols can be performed when bit value is 1.If two bits are used, interleaving with interleaving depth of 0 or nointerleaving is performed when bit value is 00 and interleaving havingdepth of OFDM symbols used in preamble symbols can be performed when bitvalue is 01. Interleaving having depth of four OFDM symbols can beperformed when bit value is 10. Interleaving having depth of eight OFDMsymbols can be performed when bit value is 11.

A receiver, specifically, FEC header decoder r1012-L1 on L1 path shownin FIG. 91 can extract Time Interleaving (TI) parameters shown in FIG.96. Using the parameters, Time de-interleaver r1010-L1 can performde-interleaving according to interleaving depth. Parameters that aretransmitted in L1 header are L1 information size (15 bits), timeinterleaving parameter (maximum 2 bits), and CRC (max 2 bits). IfReed-Muller code RM (16, 32) is used for encoding L1 header signalingfield, because bits that can be transmitted are 16 bits, not enoughnumber of bits exist. FIG. 97 shows an example of L1 signaling fieldthat can be used for such a case.

FIG. 97 shows a processing performed at FEC header 705-L1 on L1 path ofFIG. 90. In FIG. 97( a), L1( ) in the signaling fields column representsL1 size and TI( ) represents size for time interleaving parameters. Forthe first case or when L1 size (15 bits) and TI(1 bit) are transmitted,additional padding may not be necessary and substantial decodingperformance of L1 header can be obtained, however, because informationwhether to perform a time interleaving or not is transmitted, for ashort L1 block, interleaving effect cannot be obtained.

For the second case or when L1 size is reduced to ⅛ of original size,transmitting information with numbers of bits such as L1(12 bits), TI(2bits), and CRC(2 bits) becomes possible. Thus, for the second case, bestL1 decoding performance and time interleaving effect can be expected.However, the second case requires additional padding process to make L1size a multiple of eight if L1 size is not a multiple of eight. FIG. 97(b) represents padding method that can be performed at L1 signal 700-L1of FIG. 90. It shows that padding is located after L1 block and coveredwith CRC encoding. Consequently, at a receiver, FEC decode BCH/LDPCr715-L1 on L1 path of FIG. 91 can perform FEC decoding, then if there isno error when CRC field is checked, bit parsing according to L1signaling field can be performed, then a process defining rest of bitsas padding or CRC32 and excluding the rest of bits from parameters isrequired.

For the third case or when L1 size is expressed as a number of QAMmapped cells, not a number of bits, number of bits can be reduced. Forthe fourth case, L1 size is expressed not as a size of a whole L1 block,but as an L1 size per each OFDM symbol. Thus, for a receiver to obtain asize of a whole L1 block, multiplying size of L1 block in a single OFDMsymbol by a number of OFDM symbols used in preamble needs to beperformed. In this case, actual L1 size needs to exclude padding.

For the fifth case, by expressing L1 block not as a number of bits butas a number of QAM mapped cells, more reduction in bits is possible. Forthe third through fifth cases, TI, CRC parameters, and a number ofnecessary padding bits are shown. For a case where L1 block size isexpressed as a number of cells, for a receiver to obtain L1 size inbits, the receiver needs to multiply a number of bits where only cellsare transmitted by a received L1 size. In addition, a number of paddingbits needs to be excluded.

The last case shows an increased total number of bits to 32 bits byusing two RM code blocks in header. A total CRC fields become four bitsbecause each RM code block needs two bits of CRC field. A receiver orFEC header decoder r1012-L1 on L1 path of FIG. 91, needs to obtainnecessary parameters by performing FEC decoding on a total of two FECblocks. Using the obtained parameters, a receiver, specifically timedeinterleaver r1010-L1 on L1 path of FIG. 91, can determine whether toperform de-interleaving or not and can obtain a de-interleaving depth,if de-interleaving is determined to be performed. In addition, FECdecode BCH/LDPC r715-L1 can obtain LDPC block length required to performFEC decoding and shortening/puncturing parameters. Unnecessary paddingfields required to send L1 signal to a system controller can be removed.

FIG. 92 shows an example of a data slice Time Interleaving (TI). The TIprocess assumes all pilot positions are known. The TI can output onlydata cells, excluding pilots. Knowing pilot positions enables correctnumber of output cells for each OFDM symbol. Also, TI can be implementedby a single buffer at a receiver.

FIG. 93 shows an example of an efficient implementation of TimeDe-interleaver at a receiver. FIG. 93( a) shows four differentde-interleaving schemes according to an embodiment of the presentinvention. FIG. 93( b) shows a single buffer which performs thede-interleaving. FIG. 93( c) shows an exemplary scheme to address L1blocks in a 2D matrix or a 1D sequence.

As shown in FIGS. 93( a) to 93(c), using a single buffer algorithm canbe more efficient implementation of time de-interleaver. The algorithmcan be characterized by reading output cells from memory first, thenwriting input cells where output cells are read. Diagonal addressing canbe regarded as a circular addressing in each column.

More specifically, referring to FIG. 93( a), these four writing andreading method sequentially apply to the C2 frames which are received ata receiver. The first received frame at a receiver is written into thede-interleaver memory in FIG. 93( b) in the way for the 0^(th) block inFIG. 93( a) and read out in the way for the 1^(st) block. The secondreceived frame is written into the deinterleaver memory in FIG. 93( b)in the way for the 1^(st) block and read out for the 2^(nd) block. Thethird received frame is written into the de-interleaver memory in FIG.93( b) in the way for the 2^(nd) block and read out in the way for the3^(rd) block. The fourth received frame is written into thede-interleaver memory in FIG. 93( b) in the way for the 3^(rd) block andread out in the way for the 0^(th) block, and so on. That is, write andread out methods in FIG. 93( a) can be sequentially and cyclicallyapplied to the C2 frames which are received sequentially.

Time interleaving (TI) process can be performed on preambles as shown inFIG. 94. Pilot positions are periodical and easily removed and nointerleaving is necessary for L1 block header. It is because preambleheader carries TI parameters and both interleaving and non-interleavinghave same results due to repetition. Thus, only L1 signaling cells areinterleaved. Single buffer used in data slice TI can be applied.

FIG. 95 shows preamble Time Interleaving/Deinterleaving Flow.Interleaving can be performed within one L1 block, instead of wholepreamble. At a transmitter, as shown in FIG. 128 a, L1 block can beencoded {circle around (1)} then an interleaving can be performed withinthe L1 block {circle around (2)}, and the interleaved L1 block can berepeated within a preamble. At a receiver, as shown in FIG. 128 b, froma received preamble {circle around (1)}, L1 block can be combined orsynchronized and a single period of L1 block can be obtained {circlearound (2)}, and the combined L1 block can be de-interleaved {circlearound (3)}.

FIG. 96 shows a Time interleaving depth parameters in L1 headersignaling. For L1 header structure, RM (16, 32) has 16 bits capacity. Amaximum of 2 bits of CRC may improve RM BER performance. Requiredsignaling fields of L1 header are L1_info_size (15 bits) which canrequire maximum of 5 OFDM symbols and TI_depth (2 bits or 1 bit).However, a total of 18 or 19 bits exceed the capacity of L1 header.

FIG. 97 shows an example of L1 header signaling and a structure and apadding method.

FIG. 98 shows an example of an L1 signaling transmitted in a frameheader. L1 signaling information can be used as decoding parameters at areceiver. Especially, modules on L1 signal path of FIG. 91 can performL1 signaling decoding and modules on PLP path of FIG. 91 can useparameters, thus, services can be decoded. A receiver can obtainparameters of L1 signaling from signals of L1 path which are decodedaccording to an order of each field and field length. The followingsexplain meaning of each field and its use. A name of each field, anumber of bits for each field, or an example of each field can bemodified.

Num_chbon: This field indicates a number of channels used in a channelbonding. Using this field, a receiver can obtain a total bandwidth ofused channels. Channel can have 6 MHz, 7 MHz, 8 MHz, or other values ofbandwidth.

Num_dslice: This field indicates a number of data slices existing in abonded channel. After L1 signaling decoding, a receiver accesses a loopwhere information of data slices is contained, to obtain data sliceinformation. Using this field, a receiver can obtain a size of the loopfor decoding.

Num_notch: This field indicates a number of notch bands existing in abonded channel. After L1 signaling decoding, a receiver accesses a loopwhere information of notch band is contained, to obtain notch bandinformation. Using this field, a receiver can obtain a size of the loopfor decoding.

For each data slice, dslice_id, dslice_start, dslice_width,dslice_ti_depth, dslice_type, dslice_pwr_allocation, and PLP informationcan be transmitted in a preamble of a frame header. Data slice can beconsidered as a specific bandwidth which contains one or more PLPs.Services can be transmitted in the PLPs. A receiver needs to access dataslice which contains a specific PLP, to decode a service.

Dslice_id: This field can be used for data slice identification. Eachdata slice in a bonded channel can have a unique value. When a receiveraccesses one of PLPs to decode services, this field can be used for thereceiver to differentiate a data slice where the PLP is located, fromother data slices.

Dslice_start: This field indicates a start location of a data slicewithin a bonded channel. Using this field, a receiver can obtain afrequency where the data slice starts. In addition, tuning to access adata slice can be performed using this field.

Dslice_width: This field indicates a bandwidth of a data slice. Usingthis field, a receiver can obtain a size of a data slice. Especially,this field can be used in time-de-interleaving to enable decoding. Alongwith dslice_start field, a receiver can determine which frequency todecode from received RF signals. This process can be performed at Tunerr700 of FIG. 91. Information such as dslice_start and dslice_width canbe used as Tuner(r700) control signal.

Dslice_ti_depth: This field indicates time-interlaver depth used on timeinterleaving data slices. Along with dslice_width, a receiver can obtaina width and a depth of a time-deinterleaver and can perform timede-interleaving. FIG. 99 shows an example of a dslice_ti_depth. In theexample, 1, 4, 8, or 16 of OFDM symbols are used in time-interleaving.This is performed at time de-interleaver r710 of FIG. 91. Dslice_widthand dslice_ti_depth can be used as control signal.

Dslice_type: This field indicates a type of a data slice. Type1 dataslice has a single PLP within it and the PLP is a CCM (constant codingand modulation) applied. Type2 data slice represents all other kinds ofdata slices. Using this field, a receiver can perform decoding accordingto PLP. PLP of type1 does not have FECFRAME header, thus a receiver doesnot look for FECFRAME header. For type2, a receiver looks for FECFRAMEheader of PLP to obtain MODCOD information. FIG. 100 shows an example ofdslice_type. Using this field, data slice parser r711 of FIG. 91 cancontrol FEC header decoder r712-c, k.

Dslice_pwr_allocation: This field indicates a power of a data slice.Each data slice can have a different power from other data slices. It'sfor link adaption on cable system. A receiver can use this field tocontrol power of received data slice. Tuner r700 of FIG. 91 can adjustsignal gain using this field.

Num_plp: This field indicates a number of PLPs in a data slice. After L1signaling decoding, a receiver accesses a loop which includes PLPinformation. Using this field a receiver can obtain a size of the loopand decode PLPs.

For each PLP, plp_id, plp_type, PSI/SI reprocessing, plp_payload_type,plp_modcod, and plp_start_addr can be transmitted in a frame header(preamble). Each PLP can transmit one or more streams or packets such asTS and GSE. A receiver can obtain services by decoding PLPs whereservices are transmitted.

Plp_id: This field is a PLP identifier and has a unique value for eachPLP in a bonded channel. Using this field, a receiver can access PLPwhere a service to decode exists. This field can serve an identicalpurpose with plp_id transmitted in a FECFRAME header. FEC Header decoderr712-c, k of FIG. 91 can access necessary PLP using this field.

Plp_type: This field indicates whether a PLP type is a common PLP or adata PLP. Using this field, a receiver can find common PLP and canobtain information required for decoding a TS packet from the commonPLP. Further, the receiver can decode a TS packet within a data PLP.FIG. 101 shows an example of plp_type.

PSI/SI reprocessing: This field indicates whether a PSI/SI of a receivedsignal is reprocessed or not. Using this field, a receiver can determinewhether to refer PSI/SI of a specific service from a transmittedservice. If a receiver cannot refer PSI/SI of a specific service from atransmitted service, PSI/SI that can be referred by a specific servicecan be transmitted through common PLP, for example. Using thisinformation, a receiver can decode services.

Plp_payload_type: This field indicates type of payload data that PLPtransmits.

A receiver can use this field before decoding data within PLPs. If areceiver cannot decode specific type of data, decoding a PLP thatcontains that specific type of data can be prevented. FIG. 102 shows anexample of plp_payload_type. If a data slice has a single PLP and a CCMis applied to the data slice i.e., type1 data slice, fields such asplp_modcod and plp_start_addr can be transmitted additionally.

Plp_modcod: This field indicates modulation type and FEC code rate usedon PLP. Using this field, a receiver can perform QAM demodulation andFEC decoding. FIG. 103 shows an example of plp_modcod. Those valuesshown in the figure can be used in modcod that is transmitted in aheader of a FECFRAME. Symbol Demapper r713-c, k and FEC Decode BCH/LDPCr715-c, k of FIG. 91 can use this field for decoding.

Plp_start_addr: This field indicates where a first FECFRAME of a PLPappears in a transmission frame. Using this field, a receiver can obtaina start location of FECFRAME and perform FEC decoding. Using this field,Data slice Parser r711 of FIG. 91 can synchronize FECFRAMEs for type1PLPs. For each notch band, information such as notch_start andnotch_width can be transmitted in a frame header (preamble).

Notch_start: This field indicates a start location of a notch band.Notch_width: This field indicates a width of a notch band. Usingnotch_start and notch_width, a receiver can obtain a location and a sizeof a notch band within a bonded channel. In addition, a tuning locationfor a correct service decoding can be obtained and an existence of aservice within a certain bandwidth can be checked. Tuner r700 of FIG. 91can perform tuning using this information.

GI: This field indicates guard interval information used in a system. Areceiver can obtain guard interval information using this field.Time/Freq Synchronizer r702 and GI remover r704 of FIG. 91 can use thisfield. FIG. 104 shows an example.

Num_data_symbols: This field indicates a number of data OFDM symbols,except preamble, used in a frame. A transmission frame length can bedefined by this field. Using this field, a receiver can predict alocation of a following preamble, thus, this field can be used fordecoding L1 signaling. Frame Parser r708 of FIG. 91 can use this fieldand predict OFDM symbols that are preamble and send signal to preambledecoding path.

Num_c2_frames: This field indicates a number of frames existing in asuper frame. Using this field, a receiver can obtain a boundary of asuper frame and can predict information repeated by each super frame.

Frame_idx: This field is a frame index and is reset for each superframe. Using this field, a receiver can obtain a current frame numberand find a location of the current frame within a super frame. Usingthis field, Frame parser r708 of FIG. 91 can find out how many framesare ahead of a current frame in a super frame. Along with num_c2_frames,change occurring in a L1 signaling can be predicted and L1 decoding canbe controlled.

PAPR: This field indicates whether a tone reservation to reduce a PAPRis used or not. Using this field, a receiver can process accordingly.FIG. 105 shows an example. For example, if a tone reservation is used, areceiver can exclude carriers used in a tone reservation, from decoding.Specifically, Data slice parser r711 of FIG. 91 can use this field toexclude carriers from decoding.

Reserved: This field is additional bits reserved for future use.

FIG. 106 shows another example of L1 signaling transmitted in a frameheader. In FIG. 106, additionally added information to FIG. 98 can makeservice decoding by a receiver more efficient. The following fieldsexplain only the additional information. The other fields are same asthe FIG. 98.

Network_id: This field indicates a network where transmitted signalbelongs to.

Using this field, a receiver can find out a current network. When areceiver tune to another network to find a service in the network, thereceiver can process faster because using only L1 decoding is enough tomake decision whether the tuned network is a desired network or not.

C2_system_id: This field identifies a system where a transmitted signalbelongs to. Using this field, a receiver can find out current system.When a receiver tune to another system to find a service in the system,the receiver can process faster because using only L1 decoding is enoughto make decision whether the tuned system is a desired system or not.

C2_signal_start_frequency: This field indicates a starting frequency ofbonded channels. C2_signal_stop_frequency: This field indicates an endfrequency of bonded channels. Using c2_signal_start_frequency andc2_signal_stop_frequency, RF bandwidths of all data slices can be foundby decoding L1 of certain bandwidth within bonded channels. In addition,this field can be used to obtain a frequency shift amount required insynchronization of L1_XFEC_FRAMEs. L1 XFEC Combiner r1017-L1 of FIG. 91can use this field. In addition, when a receiver receives data sliceslocated at both ends of a bonded channel, this field can be used to tuneto an appropriate frequency. Tuner r700 of FIG. 91 can use thisinformation.

Plp_type: This field indicates whether a PLP is a common PLP, a normaldata PLP, or a grouped data PLP. Using this field, a receiver canidentify common PLP and can obtain information required for decoding TSpacket from the common PLP, then can decode TS packet within a groupeddata PLP. Here, the common PLP can be a PLP which contains data sharedby multiple PLPs. FIG. 107 shows an example of this field. Normal dataPLP is a data PLP that does not have common PLP. In this case, areceiver does not need to find a common PLP. Common PLP or grouped PLPcan transmit information such as plp_group_id. For the other types ofPLP, more efficient transmission is possible because no additionalinformation needs to be transmitted.

Plp_group_id: This field indicates a group where a current PLP belongsto. Grouped data PLP can transmit common TS parameters using common PLP.Using this field, if a currently decoded PLP is a grouped PLP, areceiver can find a necessary common PLP, obtain parameters required forTS packet of grouped PLP, and form a complete TS packet.

Reserved_(—)1/reserved_(—)2/reserved_(—)3: These fields are additionalbits reserved for future use for a data slice loop, a PLP loop, and atransmission frame, respectively.

FIG. 108 shows another example of L1 signaling transmitted in a frameheader. Compared to FIG. 106, more optimized information can betransmitted, thus, less signaling overhead can occur. Accordingly, areceiver can decode services efficiently. Especially, modules on L1signal path of FIG. 91 can perform L1 signaling decoding and modules onPLP path of FIG. 91 can use parameters, thus, services can be decoded. Areceiver can obtain parameters of L1 signaling from signals of L1 pathwhich are decoded according to an order of each field and field length.A name of each field, a number of bits for each field, or an example ofeach field can be modified. Descriptions of fields except dslice_widthare identical to aforementioned descriptions of fields. A function ofdslice_width according to an example is as follows.

Dslice_width: This field indicates a bandwidth of a data slice. Usingthis field, a receiver can obtain a size of a data slice. Especially,this field can be used in time-de-interleaving to enable decoding. Alongwith dslice_start field, a receiver can determine which frequency todecode from received RF signals. This process can be performed at Tunerr700 of FIG. 91. Information such as dslice_start and dslice_width canbe used as Tuner r700 control signal. At this point, width of a dataslice can be extended up to 64 MHz by using 12 bits for thisdslice_width field. Using this field, a receiver can determine if acurrently available tuner can decode current data slice. If a width of adata slice is bigger than a bandwidth of a legacy tuner of a receiver,to decode such a data slice, a receiver can use either at least twolegacy tuners or a tuner with a large enough bandwidth. In the example,a granularity of values used in dslice_start, dslice_width, notch_start,and notch_width can be 12 OFDM carriers (cells). In other words, areceiver can find a location of an actual OFDM cell by multiplyingtransmitted values by 12. In the example, for a granularity ofPlp_start_addr, one OFDM carrier (cell) can be used. In other words, areceiver can find out how many OFDM symbols and OFDM cells are ahead ofa start location of a PLP within an OFDM symbol. Dslice_start anddslice_width can be used for this purpose. Data slice Parser r711 ofFIG. 91 can perform such a process.

FIG. 109 shows an example of processing at FEC header 705-L1 on L1 pathof FIG. 90. A total of 16 bits can be transmitted in FEC header of a L1path. Fourteen bits can be allocated for L1_info_size. If L1_info_sizehas a value that is a half of actually transmitted L1 block length, areceiver can multiply received L1_info_size by two and obtain actuallength of L1 block and start decoding L1. This obtained length of L1block is a length that includes padding.

For L1 block that is determined to have no error though CRC check, areceiver can regard rest of bits after the L1 decoding as padding. Thelast two bits, similar as in previous methods, can be used forindicating time interleaving depth of preambles. Preamble mapper 1007-L1of FIG. 90 can determine required OFDM symbols to transmit L1 blocks.Afterwards, time interleaver 1008-L1 of FIG. 90 can perform timeinterleaving. Using the time interleaving depth information andL1_info_size, a receiver can find out what size of L1 block istransmitted in how many OFDM symbols. Combining, merging, andtime-de-interleaving L1 blocks can be performed at L1 XFEC combiner12417-L1, L1_FEC Merger 12418-L1, and Time de-interleaver 12410-L1 ofFIG. 91, respectively.

At a receiver in FIG. 91, a length of an L1 XFEC block within an OFDMsymbol can be obtained by dividing a total L1 block length by a numberof OFDM symbols used in a preamble. The number of OFDM symbols can beobtained from a valued defined in ti_depth. L1 XFEC combiner 12417-L1 ofa receiver can obtain L1 XFEC block. Then, Time de-interleaving 12410-L1can be performed using ti_depth. Finally, L1 XFEC blocks can be mergedto obtain an L1_FEC block. After L1_FEC Merger 12418-L1, bitDe-interleaving r714-L1, and LDPC/BCH decoding r715-L1, L1 block can beobtained. L1_info_size can be multiplied by two, L1 block can be CRCchecked, and L1 can be decoded. Unnecessary padding can be disregarded.

FIG. 110 shows another example of L1 signaling transmitted in a frameheader. Compared to FIG. 108, numbers of bits for some fields aremodified and some fields are added to improve an efficiency of servicedecoding by a receiver. Especially, modules on L1 signal path of FIG. 91can perform L1 signaling decoding and modules on PLP path of FIG. 91 canuse parameters, thus, services can be decoded. A receiver can obtainparameters of L1 signaling from signals of L1 path which are decodedaccording to an order of each field and field length. A name of eachfield, a number of bits for each field, or an example of each field canbe modified. Except modified fields from previous figure, descriptionsof fields are identical to aforementioned descriptions of fields.RESERVED_(—)1, RESERVED_(—)2, RESERVED_(—)3, and RESERVED_(—)4 arefields reserved for future use. In the example, PLP_START can indicateidentical information with aforementioned plp_start_addr.

L1 PART2_CHANGE_COUNTER indicates a number of frames from first frame toa frame that has a change in any of the L1 signaling information,excluding change in PLP_START, from previous frames. That is, this fieldindicates the number of frames ahead where the configuration willchange. Using this field, a receiver can skip decoding L1 for each frameto get L1 information. In other words, by using the value ofL1_PART2_CHAGNE_COUNTER, a receiver can determine which frame has achange in L1 information from previous frames, thus, no L1 decoding isperformed for frames before a frame with change in L1 occurs, then L1decoding can be performed for the frame that has change in L1. Thus,unnecessary operations can be skipped. Using this field, a receiver canavoid the redundant L1 decoding operation. This value can be alsocalculated by a receiver with already decoded L1 information.

If L1_PART2_CHANGE_COUNTER is 0, it means there has not been a change inL1 for at least 256 (2̂8, 8 is a number of bits used forL1_PART2_CHANGE_COUNTER) frames. In this one of best cases, a receiverneeds to decode L1 only every 51 seconds. This process can be performedat Frame Parser r708 of FIG. 91. Frame Parser can determine if currentpreamble has a change in L1 and can control subsequent processes on L1signal path. A receiver can calculate PLP_START for specific frame fromalready obtained PLP_START and PLP_MODCOD, without performing L1decoding to obtain PLP_START.

FIG. 111 shows examples of fields shown in FIG. 110. Blocks of areceiver can perform processes according to the values indicated by thefields in the examples.

FIG. 112 shows another example of L1 signaling transmitted in a frameheader. Compared to FIG. 110, some fields are modified and some fieldsare added to improve an efficiency of service decoding by a receiver.Especially, modules on L1 signal path of FIG. 91 can perform L1signaling decoding and modules on PLP path of FIG. 91 can useparameters, thus, services can be decoded. A receiver can obtainparameters of L1 signaling from signals of L1 path which are decodedaccording to an order of each field and field length. A name of eachfield, a number of bits for each field, or an example of each field canbe modified. Except modified fields from previous figure, descriptionsof fields are identical to aforementioned descriptions of fields.

Descriptions of DSLICE_START, DSLICE_WIDTH, NOTCH_START, and NOTCH_WIDTHare identical with previous descriptions. However, signaling overheadcan be minimized by signaling the fields with a minimum number of bitsaccording to GI mode. Accordingly, it can be said that signaling ofDSLICE_START, DSLICE_WIDTH, NOTCH_START, and NOTCH_WIDTH is based uponGI mode. L1 information can be obtained from L1 signal path of areceiver of FIG. 91. A system controller can determine a number of bitsused for each field according to obtained GI value and can read thefields accordingly. GI value needs to be transmitted before othervalues.

Instead of DSLIC_START and DSLICE_WIDTH, 12 bits of tuning positionwhich indicates an optimized location to obtain data slice and 11 bitsof offset value from a tuning position to indicate a width of a dataslice can be transmitted. Especially, by using 11 bits of offset value,data slices that occupy a maximum of 8 bonded channels can be signaledand a receiver that can receive such data slices can operateappropriately. A tuner r700 of a receiver of FIG. 91 can determine RFbandwidth using a tuning position and can obtain a width of a data sliceusing offset value, to serve a same purpose as the aforementionedDSLICE_WIDTH.

DSLICE_CONST_FLAG is a field for indicating whether a configuration of aspecific data slice is maintained as a constant. Using this fieldobtained from an L1 from a certain bandwidth, a receiver can determineif a specific data slice has a constant configuration, then the receivercan receive PLPs of the specific data slice without additional L1decoding. This kind of process can be useful for receiving data slicethat is located in a bandwidth where L1 decoding is not available.

DSLICE_NOTCH_FLAG is a field or a flag for indicating notch bands atboth edges of a specific data slice. Most Significant Bit (MSB) can beused as an indicator for notch band neighboring at a low bandwidth andLeast Significant Bit (LSB) can be used as an indicator for notch bandneighboring at a high bandwidth. Using the field, when a receiverdecodes a specific data slice, the receiver can take into account of anotch band by finding out changes in active carriers caused by continualpilots neighboring at both ends of a notch band. This information canalso be obtained from notch information transmitted in NOTCH_START andNOTCH_WIDTH. Time De-interleaver r710 of a receiver of FIG. 91 can usethe information to find location of active carriers and send data onlycorresponding to the active carriers, to a data slice parser.

For PLP_TYPE, one additional bit is added to FIG. 110. FIG. 113 shows anexample of PLP_TYPE of FIG. 112. A value indicating bundled data PLP canbe transmitted. A large TS stream having a high data rate can bemultiplexed into multiple PLPs. Bundled data PLP can be used forindicating PLPs where multiplexed streams are transmitted. For a legacyreceiver which is unable to decode a specific PLP, this field canprevent the receiver from accessing the PLP, thus, a possiblemalfunction can be prevented.

Yet as an alternative method, if the aforementioned dslice_width is usedalong with dslice_start field and notch information, a receiver candetermine which frequency to decode from received RF signals. Thisprocess can be performed at Tuner (r700) of FIG. 91. Information such asdslice_start, dslice_width, notch_start, and notch_width can be used asTuner r700 control signal. Thus, obtaining a data slice andsimultaneously tuning to an RF band where no L1 decoding problems existcan become possible, by avoiding notch.

Regarding L1 signaling of FIG. 112, FIG. 114 shows a relationshipbetween L1 signaling and L2 signaling when a PLP is bundled type. Inaddition, FIG. 114 also shows an action that can be taken by a receiverfor such a case. TS1 can be mapped into PLP37 through c2dsd of L2. ThisTS1 corresponds to a normal PLP of L1, thus, the PLP can be decoded by anormal receiver (single 8 MHz tuner) and a premium receiver (multipletuner or wideband (>8 MHz) tuner). TS2 and TS3 are mapped into PLP39 andPLP44 respectively, through c2dsd. These correspond to bundled PLP ofL1, thus, these PLPs can be decoded by a premium receiver (multipletuner or wideband (>8 MHz) tuner) but not by a normal receiver (single 8MHz tuner). Consequently, according to L1 information, a receiver cancheck if corresponding TS is received or not.

FIG. 115 and FIG. 116 are flowcharts describing L1 decoding and L2decoding actions for bundle PLP type and normal PLP type in a normalreceiver and a premium receiver, respectively. FIG. 117 shows an exampleof c2_delivery_system_descriptor structure and syntax for L2 signalingwhile taking into account of FIG. 112. This descriptor can map TS_idinto plp_id as shown in FIG. 114. Bundle information can be processed inL1, thus, it needs not be signaled in L2. The variables shown in FIG.117 are described as follows.

Plp_id: This 8-bit field uniquely identifies a data PLP within a C2System.

C2_system_id: This 16-bit field uniquely identifies a C2 system. Theremaining part of this descriptor, immediately following theC2_system_id field is only present once per C2 system, because theparameters are uniquely applicable to all data slices carried over aparticular C2 System. A presence or absence of that part can be derivedfrom the descriptor length field. In the absence of the remaining part,this length equals 0x07, otherwise a larger value is assigned.

C2_System_tuning_frequency: This 32-bit field indicates a frequencyvalue. The coding range can be from minimum 1 Hz (0x00000001) up to amaximum of 4, 294, 967, 295 Hz (0xFFFFFFFF). This data field can give atuning frequency, where a complete Preamble is transmitted within thetuning window. Generally the C2_System_tuning_frequency is the centerfrequency of a C2_System, but it may deviate from the center frequencyin case notches exist in this area.

Active_OFDM_symbol_duration: This 3-bit field indicates a duration ofthe active OFDM symbol. An example is shown in FIG. 118.

Guard_interval: This 3-bit field indicates a guard interval. An exampleis shown in FIG. 119.

In the previous examples of L1 time interleaving/deinterleaving, forcases when TI_DEPTH is “10” or “11”, Preamble mapper 1007-L1 of FIG. 90can evenly divide original L1 block into four or eight sub-blocks.However, if a size of the sub-block is smaller than a minimum sizerequired to perform an FEC encoding, the FEC encoding may not beperformed appropriately. A possible solution can be setting a threshold.If a size of an L1 block is smaller than a set threshold, L1 block canbe repeated for four or eight times for cases when TI_DEPTH is “10” or“11”. If a size of an L1 block is bigger than a set threshold, L1 blockcan be evenly divided into four or eight sub-blocks. The threshold canbe set as four or eight times of a minimum size required to perform anFEC encoding.

In addition, setting TI_DEPTH as “10” or “11” is for cases when timeinterleaving effect is not obtained because of a small L1 block size.Thus, the threshold can be defined as a size of information bits thatcan be transmitted by a single preamble symbol. For example, if anidentical L1_FEC encoding with DVB-T2 is assumed, a threshold will be4,772 bits.

For cases when TI_DEPTH is “10” or “11”, using L1 size information, TIdepth, and a threshold value shared between a transmitter and areceiver, modules of a receiver, from FEC header decoder r1012-L1 toL1_FEC_Merger r1018-L1 of FIG. 91 can determine a size of L1 sub-block,combining, and merging the L1 sub-blocks that are transmitted in an OFDMsymbol of a preamble.

If an L1 size is smaller than a threshold value, L1_FEC_Merger r1018-L1of FIG. 91 does not need to merge divided sub-blocks because theoriginal L1 block is repeatedly transmitted according to a TI_DEPTH infour or eight OFDM symbols. However, if an L1 size is bigger than athreshold value, because a number of symbols that is more than a numberof OFDM symbols required to transmit L1 block is used, FEC headerdecoder r1012-L1 of FIG. 91 can obtain a size of a sub-block usingTI_DEPTH. Then, L1_FEC combiner r1017-L1 can combine L1_FEC blocks andtime deinterleaver r1010-L1 can perform de-interleaving. Finally, L1_FECmerger r1018-L1 can merge L1_FEC blocks to restore original L1 block.

FIG. 120 shows another example of L1 signaling that is transmitted in aframe header. Compared to FIG. 112, some fields are modified and somefields are added to improve an efficiency of service decoding by areceiver. Especially, modules on L1 signal path of FIG. 91 can performL1 signaling decoding and modules on PLP path of FIG. 91 can useparameters, thus, services can be decoded. A receiver can obtainparameters of L1 signaling from signals of L1 path which are decodedaccording to an order of each field and field length. A name of eachfield, a number of bits for each field, or an example of each field canbe modified. Except modified fields from previous figure, descriptionsof fields are identical to aforementioned descriptions of fields.

DSLICE_TUNE_POS indicates a tuning position for a receiver to obtain adata slice. Depending on a GI mode, this value can be expressed in 12 or11 bits. DSLICE_OFFSET_RIGHT and DSLICE_OFFSET_LEFT which indicateoffset value from a tuning position or a width of a data slice, can beexpressed in 9 or 8 bits, depending on a GI mode. If the offset can havea signed value, i.e., a positive or a negative value, a position and awidth of a data slice having a narrow band can also be expressed. Tunerr700 of a receiver in FIG. 91 can determine an RF band using a tuningposition, then using this signed offset value, data slice width can beobtained. Thus, this field can serve a same purpose as aforementionedDSLICE_WIDTH. A receiver can obtain Bit-width using a GI value.

DSLICE_NOTCH_FLAG is a flag indicating that a certain data slice isadjacent to a notch band. It can serve a same purpose as aforementionedexamples but here, only 1 bit is used for this field per each dataslice. Using this 1 bit information, a receiver can perform samefunction as aforementioned examples.

PLP_BUNDLED_FLAG indicates that a PLP is a bundled data PLP. That is,PLP_BUNDLED_FLAG indicates whether or not a PLP is a bundled with otherPLP within a broadcasting system. This field can serve a same purpose asaforementioned bundled data PLP of PLP_TYPE of FIG. 112. PLP_TYPE isshown in FIG. 110.

FIG. 121 is showing another two examples of time interleaving that canbe used on L1 path of FIG. 90. As seen in the Time interleaving ON (1),interleaving can be only block interleaving. Compared to the methodshown in FIG. 83, frequency interleaving performance may not be as goodas the method shown in FIG. 83. However, for cases when TI_DEPTH is “10”or “11”, without repeating or dividing L1 blocks according to athreshold, L1 blocks can be spread in a time direction regardless of L1block size then can be repeated in a preamble if there is a room in thepreamble, thus, this method can be advantageous in that a control can besimplified. The interleaving can be performed by writing input symbolstreams in a time direction and reading the written symbol streams in afrequency direction. Time deinterleaver r1010-L1 on L1 path of areceiver of FIG. 91 can perform de-interleaving by writing input symbolstreams in a frequency direction and reading the written symbol streamsin a time direction.

A second example or the Time interleaving ON (2) of FIG. 121 includesadditional process to the Time interleaving ON (1), which is acircular-shifting in a row direction. By this process, in addition toadvantages from the Time interleaving ON (1), an effect of spreading ina frequency domain can be obtained. Time deinterleaver r1010-L1 on L1path of a receiver of FIG. 91 needs to perform circularly re-shifting ina row direction before performing the process of the Time interleavingON (1).

Using the suggested methods and devices, among others advantages it ispossible to implement an efficient digital transmitter, receiver andstructure of physical layer signaling.

By transmitting ModCod information in each BB frame header that isnecessary for ACM/VCM and transmitting the rest of the physical layersignaling in a frame header, signaling overhead can be minimized.

Modified QAM for a more energy efficient transmission or a morenoise-robust digital broadcasting system can be implemented. The systemcan include transmitter and receiver for each example disclosed and thecombinations thereof.

An Improved Non-uniform QAM for a more energy efficient transmission ora more noise-robust digital broadcasting system can be implemented. Amethod of using code rate of error correction code of NU-MQAM and MQAMis also described. The system can include transmitter and receiver foreach example disclosed and the combinations thereof.

The suggested L1 signaling method can reduce overhead by 3-4% byminimizing signaling overhead during channel bonding.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the invention.

1. A method for transmitting broadcast signals, the method comprising:LDPC (Low Density Parity Check) encoding broadcast data that is carriedby a physical path; LDPC encoding signaling data, the LDPC encodedsignaling data including a group identifier field for identifying agroup to which a current physical path belongs; time interleaving theLDPC encoded broadcast data by a twisted fashion; building at least onesignal frame by assembling the time interleaved broadcast data and theLDPC encoded signaling datas; and transmitting the broadcast signalsincluding the built at least one signal frame.
 2. The method of claim 1,wherein the time interleaving is based on a skip operation.
 3. Themethod of claim 1, wherein: the at least one signal frame includes atleast one preamble symbol; and the LDPC encoded signaling data isrepeated in the at least one preamble symbol.
 4. The method of claim 1,further comprising bit interleaving the LDPC encoded broadcast data. 5.The method of claim 1, wherein the LDPC encoded signaling data furtherincludes time interleaving information.
 6. An apparatus for transmittingbroadcast signals, the apparatus comprising: an encoder for LDPC (LowDensity Parity Check) encoding broadcast data that is carried by aphysical path; a signaling encoder for LDPC encoding signaling data, theLDPC encoded signaling data including a group identifier field foridentifying a group to which a current physical path belongs; a timeinterleaver for time interleaving the LDPC encoded broadcast data by atwisted fashion; a frame builder for building at least one signal frameby assembling the time interleaved broadcast data and the LDPC encodedsignaling data; and a transmitter for transmitting the broadcast signalsincluding the built at least one signal frame.
 7. The apparatus of claim6, wherein the time interleaving is based on a skip operation.
 8. Theapparatus of claim 6, wherein: the at least one signal frame includes atleast one preamble symbol; and the LDPC encoded signaling data isrepeated in the at least one preamble symbol.
 9. The apparatus of claim6, further comprising a bit interleaver for bit interleaving the LDPCencoded broadcast data.
 10. The transmitter of claim 6, wherein the LDPCencoded signaling data further includes time interleaving information.11. A method for receiving broadcast signals, the method comprising:receiving the broadcast signals; parsing at least one signal frame fromthe received broadcast signals, the at least one signal frame includingsignaling data and broadcast data, the broadcast data carried by aphysical path and the signaling data including a group identifier fieldfor identifying a group to which a current physical path belongs;decoding the signaling data; time deinterleaving the broadcast data by atwisted fashion; and LDPC (Low Density Parity Check) decoding the timedeinterleaved broadcast data.
 12. The method of claim 11, wherein thetime deinterleaving is based on a skip operation.
 13. The method ofclaim 11, wherein: the at least one signal frame further includes atleast one preamble symbol; and the signaling data is repeated in the atleast one preamble symbol.
 14. The method of claim 11, d furthercomprising bit deinterleaving the time deinterleaved broadcast data. 15.The method of claim 11, wherein the signaling data further includes timedeinterleaving information.
 16. An apparatus for receiving broadcastsignals, the apparatus comprising: a receiver for receiving thebroadcast signals; a frame parser for parsing at least one signal framefrom the received broadcast signals, the at least one signal frameincluding signaling data and broadcast data, the broadcast data carriedby a physical path and the signaling data including a group identifierfield for identifying a group to which a current physical path belongs;a signaling decoder for decoding the signaling data; a timedeinterleaver for time deinterleaving the broadcast data by a twistedfashion; and a decoder for LDPC (Low Density Parity Check) decoding thetime deinterleaved broadcast data.
 17. The apparatus of claim 16,wherein the time deinterleaving is based on a skip operation.
 18. Theapparatus of claim 16, wherein: the at least one signal frame furtherincludes at least one preamble symbol; and the signaling data isrepeated in the at least one preamble symbol.
 19. The apparatus of claim16, further comprising a bit deinterleaver for bit deinterleaving thetime deinterleaved broadcast data.
 20. The apparatus of claim 16,wherein the signaling data further includes time deinterleavinginformation.